The Microscope. Its History, Construction, And Application 15th Ed. - free ebook by Jabez Hogg

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The Microscope. Its History, Construction, And Application 15th Ed.

Jabez Hogg

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PREFACE TO THE FIFTEENTH EDITION.

PREFACE TO THE FIFTEENTH EDITION.

The First Edition of this work appeared in 1854, a time in the history of the Microscope when the instrument, as an aid to original scientific research, may be said to have been in its infancy. Then certainly it was seldom employed in the laboratory or the medical schools. Now, however, as I anticipated, it has asserted its proper position, and has at length become one of the most important auxiliaries to science, and a direct incentive to original work, while it has doubtless exercised consider

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PREFACE TO THE FIRST EDITION.

PREFACE TO THE FIRST EDITION.

The Author of this Publication entered upon his task with some hesitation and diffidence; but the reasons which influenced him to undertake it may be briefly told, and they at once explain his motives, and plead his justification, for the work which he now ventures to submit to the indulgent consideration of his readers. It had been to him for some time a subject of regret that one of the most useful and fascinating studies—that which belongs to the domain of microscopic observation—should be, i

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FRONTISPIECE.

FRONTISPIECE.

In this Plate Fig. 1 shows the elegant lattice-sphere of Rhizosphæra; Fig. 2 represents Sphærozoum, whose skeleton consists of loose spicules, arranged tangentially; Actinomma, Fig. 3, possesses three concentric lattice-spheres, joined by radiating spines; Figs. 4, 5, and 6, represent Lithomespilus, Ommatocampe, and Carpocanium; Fig. 7 represents a deep-sea form (Challengeria), whose oval case is formed of a regular, very fine-meshed, network; Fig. 8 depicts the elegant lattice-sphere of Heliosp

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PLATE I.—Page 400.

PLATE I.—Page 400.

Fig. 1. Peziza bicolor—2. Truffle: a. ascus of spores; b. mycelium—3. Sphæria herbarum: a. piece of dead plant, with S. herbarum natural size; b. section of same, slightly magnified; d. Ascus with spores, and paraphyses more magnified—4. Peziza pygmæa—5. Apical form of same—6. P. corpulasis: Ascus with spores and paraphyses, merely given as a further illustration of structure in Peziza—7. Yeast healthy—8. Yeast exhausted—9. Phyllactinia guttata—10. Yeast with favus spores and mycelium of fungus—

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PLATE II.—Page 412.

PLATE II.—Page 412.

Fig. 27. Ceramium acanthonotum—28. Closterium, Triploceras gracilis—29. Cosmarium radiatum—30. Micrasterias denticulata—31. Docidium pristidæ—32. Callithamnion plumula—33. Diatoma, living: a. Licmophora splendida; b. Achnanthes longipes; c. Grammatophora marina. These figures are intended to show the general character of the endochrome and growth of frustule—34. Callithamnion refractum—35. Jungermannia albicans; b. representing elater and spores—36. Leaf with antheridia, or male elements, repres

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PLATE III.—Page 479.

PLATE III.—Page 479.

Figs. 43, 44, 45, 46, 47, 48, 49, 50, 51, 52. These figures are from drawings made by Major Owen, to illustrate forms of living Polycystina, sketched from life; these convey a faint idea of the richly coloured appearance of the natural structure; Figs. 48 to 52—53. Gregarina lumbricorum, round form—54. Gregarina lumbricorum, the usual elongated form—55. Gregarina serpulæ—56. Gregarina Sieboldii; illustration of septate form, with reflexed hook-like processes—57. Gregarina lumbricorum, encysted—5

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PLATE IV.—Page 514.

PLATE IV.—Page 514.

Fig. 86. Hartea elegans—87. Side view of Synapta spicula—88. Ophioglypha rosula (very immature specimen): a. Claw hooks; b. palmate spicula. The development of this species is described by G. Hodge, in “Transactions of Tyneside Naturalists’ Field-Club”—89. Spine of a star-fish, particularly interesting as showing the reticular calcareous network obtaining in this as in all other hard parts of the Echinodermata—90. Very minute Spatangus, obtained from stomach of a bream: many of the spines are go

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PLATE V.—Page 556.

PLATE V.—Page 556.

Fig. 108. Velutina lævigata, portion of lingual membrane—109. Velutina lævigata, part of mandible—110. Hybocystis blennius, portion of palate—111. Sepia officinalis, portion of palate—112. Aplysia hybrida, part of mandible—113. Loligo vulgaris, part of palate—114. Haliotis tuberculatus, part of palate—115. Cistula catenata, part of palate—116. Patella radiata, part of palate—117. Acmæa virginea, part of palate—118. Cymba olla, part of palate—119. Scapander ligniarius—120. Oneidoris bilamellata,

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PLATE VI.—Page 582.

PLATE VI.—Page 582.

Fig. 124. Egg of Caradrina morpheus, mottled rustic moth—125. Egg of tortoise-shell butterfly, Vanessa urticæ—126. Egg of common footman, Lithosia complanula—127. Egg of shark moth, Cucullia umbratica—128. Maple-aphis—129. Egg shell of acarus, empty—130. Egg of house-fly—131. Mouth of Tsetse-fly, Glossina morsitans—132. Vapourer moth, Orgyia antiqua: antenna of male—133. Vapourer moth: antenna of female; a . branch more magnified to show rudimentary condition of the parts—134. Tortoise-shell but

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PLATE VII.—Page 633.

PLATE VII.—Page 633.

Fig. 149. Toe of mouse, integuments, bone of foot, and vessels—150. Tongue of mouse, showing erectile papillæ and muscular layer—151. Brain of rat, showing vascular supply—152. Vertical section of tongue of cat, fungi-form papillæ and capillary loops passing into them, vessels—153. Kidney of cat, showing Malpighian turfts and arteries—154. Small intestine of rat, with villi and layer of mucous membrane exposed—155. Nose of mouse, showing vascular supply to roots of whiskers—156. Vascular supply

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PLATE VIII.—Page 220.

PLATE VIII.—Page 220.

Fig. 158. New Red Sandstone—159. Quartz—163. Granite—161. Sulph. Copper—162. Saliginine—163. Sulph. Iron and Cobalt, crystallized in the way described by Thomas—164. Borax—165. Sulph. Nickel and Potash—166. Kreatine—167. Starch granules—168. Aspartic Acid—169. Fibro-cells, orchid.—170. Equisetum cuticle—171. Holothuria spicula, Australia—172. Holothuria spicula, Port Essington—173. Deutzia scabra; upper and under surface—174. Cat’s tongue, process—175. Prawn shell, exuvia with crystals of lime—1

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PLATE IX.—Page 362.

PLATE IX.—Page 362.

Fig. 1. Cocci, singly, and varying in size—2. Cocci in chains or rosaries (streptococcus)—3. Cocci in a mass (staphylococcus)—4 and 5. Cocci in pairs (diplococcus)—6. Cocci in groups of four (merismopedia)—7. Cocci in packets (sarcina)—8. Bacterium termo—9. Bacterium termo × 4000 (Dallinger and Drysdale)—10. Bacterium septicæmiæ hæmorrhagicæ—11. Bacterium pneumoniæ crouposæ—12. Bacillus subtilis—13. Bacillus murisepticus—14. Bacillus diphtheriæ—15. Bacillus typhosus (Eberth)—16. Spirillum undula

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PLATE X.—Page 420.

PLATE X.—Page 420.

Fig. 1. Euastrum oblongum—2. Micrasterias rotata—3. Desmidium quadrangulatum—4. Didymoprium Grevillii—5. Micrasterias, sporangium of—6. Didymoprium Borreri—7. Cosmarium Ralfsii—8, 9. Xanthidiæ—10. X. armatum—11. Cosmarium crenatum—12. C. Sphærozosma vertebratum—13, 17. Sporangia of Cosmarium—14. X. fasiculatum—18. Staurastrum hirsutum—19. Arthrodesmus convergens—15. Staurastrum tumidum—16. Staurastrum dilitatum—21. Penium—22. Euastrum Didelta—23. Docidium clavatum—24. Pediastrum biradiatum—25. C

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PLATE XI.—Page 428.

PLATE XI.—Page 428.

Fig. 1. Arachnoidiscus—2. Actinocyclus (Bermuda)—3. Cocconeis (Algoa Bay)—4. Coccinodiscus (Bermuda)—5. Isthmia enervis—6. Zygoceros rhombus—7. Campilodiscus clypeus—8. Biddulphia—9. Gallionella sulcata—10. Triceratium, found in Thames mud—11. Gomphonema geminatum, with their stalk-like attachments—12. Dictyocha fibula—13. Eunotia—14. Cocconema—15. Fragilaria pectinalis—16. Meridion circulare—17. Diatoma flocculosum....

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PLATE XII.—Page 438.

PLATE XII.—Page 438.

Taken with Zeiss’s 3 mm. N.A. 1·40 by Mr. A. A. Carvell for the Author. Fig. 1. Portion of Surirella gemma, magnified × 1,000—2. Broken Frustule of Pleurosigma angulatum, × 750—3 and 5. Triceratium favus ×—1,000—4. Navicula rhomboides × 1,300—6. Pleurosigma formosum, showing black dots—7. P. formosum, showing white dots, × 750....

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PLATE XIII.—Page 454.

PLATE XIII.—Page 454.

Fig. 1. Elementary ovid cells—2. Branching tissue—2 A and 3. Spiral vessels from Opuntia vulgaris—4. Stellate tissue, section of rush—5. Mushroom spawn—6. Starch from Tous-les-mois —7. Starch from sago—8. Starch from rice—9. Wheat-starch—10. Rhubarb starch in isolated cells—11. Maize-starch—12. Oat-starch—13. Barley-starch—14. Section of Potato cells, filled with healthy starch—15. Potato starch more highly magnified—16. Section of Potato with nearly all starch absent—17. Potato with starch dest

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PLATE XIV.—Page 472.

PLATE XIV.—Page 472.

Fig. 1. Epidermis of husk of wheat, spiral vessels and silicious crystals—2. Section of cane, silicious cell walls, internal portion filled with granular bodies—3. Cuticular layer of the onion, showing crystals of calcium carbonate and oxalate—4. Cells of garden rhubarb, with crystalline bodies and raphides—4 a . Another layer filled with starch grains—5. Section of pear, testa, sclerogenous and granular tissue—6. Stellate hairs, sinuous cells and silicious parenchyma of leaf of Deutzia scabra,

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PLATE XV.—Page 482.

PLATE XV.—Page 482.

Fig. 1. Astrorhiza limicola—2. Lieberkühnia paludosa—3. Micro-gromia socialis undergoing fission—4. A colony of Hertwig’s Micro-gromia socialis—5. G. Lieberkühnia—6. Egg-shaped Gromia, G. oviformis, with pseudopodia extended, magnified 500 diameters. “Hertwig Ueber Micro-gromia, archiv. für Mickr. Anat. bdx.”...

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PLATE XVI.—Page 510.

PLATE XVI.—Page 510.

Fig. 1. A portion of sponge, Halichondria simulans, showing silicious spicula imbedded in the sarcode matrix—2. Spicula divested of its matrix by acid—3. Gemmule Spongilla fluviatallis enclosed in spicula—4. Birotulate spicula from same—5. Gemmule after being steeped in acid showing reticulated coating of birotulate spicula—6. Gemmules of Geodia—7. Gemmule in more advanced stage of growth—8. Skeleton of the acerate form covered by rows of spines—9. Showing rings of growth and horny covering, and

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PLATE XVII.—Page 518.

PLATE XVII.—Page 518.

Fig. 1. a. Astrophyton scutatum— b. Doris pinnatifida, back and side view— c. Æquorea Forbesina— d. Medusæ bud— e. Thaumantias corynetes— f. Echinus in an early free stage— g. Echinus sphæra— h. Cydippe pyleus— i. Ascidiæ— k. Botryllus violaceus, on a Fucus— l. Corystes cassivelaunus— m. Eurynome aspera— n. Ophiocoma rosula— o. Pagurus Prideauxii— p. Ebalia Permantii....

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PLATE XVIII.—Page 558.

PLATE XVIII.—Page 558.

Fig. 1. Transverse section of spine of Echinus—2. Another section of Echinus, showing reticulated structure, the calcareous portion dissolved out by acid—3. Horizontal section of shell of Haliotis splendens, showing stellate pigment—4. Shell of crab with granules in articular layer—5. Another section of same shell, showing hexagonal structure—6. Horizontal section of coach-spring shell, Terebratulata rubicunda, showing radiating perforations—7. Transverse section of shell of the Pinna ingens—8.

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PLATE XIX.—Page 636.

PLATE XIX.—Page 636.

Fig. 1. a. Spheroidal epithelium cells, filled with central nuclei and granular matter; b. mucous membrane of stomach, showing cells, with open mouths of tubes at the bottom of each, magnified 50 diameters—2. a. Diagram of a portion of the involuted mucous membrane, showing continuation of its elements in the follicles and villi, with a nerve entering the submucous tissue. The upper surface of one villus is covered with cylindrical epithelium; the other denuded, and with dark line of basement me

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PLATE XX.—Page 658.

PLATE XX.—Page 658.

Figs. 1. and 2. Transverse section of the human clavicle (collar bone), showing Haversian canals, concentric laminæ, and concentric arrangement of bone cells—3. Transverse section of the femur of an ostrich—4. Transverse section of humerus (fore-arm) bone of a turtle, Chelonia mydas—5. Horizontal section of the lower jaw-bone of a conger eel, in which no Haversian canals are present—6. A portion of the cranium of a siren, Siren lacertina—7. Portion of bone taken from the shaft of humerus of a Pt

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ERRATA.

ERRATA.

(Professor Abbe, erroneously referred to more than once as “the late” is, the author is happy to say, in excellent health)....

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Early History of the Microscope.

Early History of the Microscope.

The instrument known as the Microscope derives its designation from two Greek words, μικρὸς ( mikros ), small , and σκοπέω ( skopeo ), to see or observe ; and is an optical instrument by means of which objects are so magnified that details invisible or indistinct to the naked eye are clearly seen. Its origin, so far as yet can be traced back, seems to be of a doubtful nature. It is tolerably certain the ancients had little or no conception of the magnifying power of lenses; this may be surmised

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The Modern Microscope.

The Modern Microscope.

To the celebrated Dr. Hooke belongs the honour of publishing an account of the compound instrument in 1665 in his “Micrographia.” His first claim, however, is founded on the application of a lamp adjustable on a pillar, together with a glass globe of water and a deep plano-convex condensing lens. By means of this arrangement, he says, “The light can be directed more directly on the object under examination.” In the further description given of his microscope, he explains: “It has four draw-tubes

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Elementary Optics.

Elementary Optics.

Value of Inductive Science—Light: Its Propagation, Refraction, Reflection—Spherical and Chromatic Aberrations—Human Eye, formation of Images of External Objects in—Visual Angle increased—Abbe’s Theory of Microscopic Vision. The advances made in physics and mechanics during the 17th and 18th centuries fairly opened the way to the attainment of greater perfection in all optical instruments. This has been particularly exemplified with reference to the invention of the microscope, as briefly sketche

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Indices of Refraction.

Indices of Refraction.

The ratio of the sine of the angle of incidence to the sine of the angle of refraction, when a ray passes from one medium to another is termed the relative index of refraction. When a ray passes from vacuum into any medium, this ratio is always greater than unity, and is called the absolute index of refraction , or simply the index of refraction for the medium in question. The absolute index of air is so small that it may be neglected in comparison with those of solids and liquids; but strictly

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Lenses.

Lenses.

Forms of Lenses. —A lens is a portion of a refracting medium bounded by two surfaces which are portions of spheres, having a common axis, termed the axis of the lens . Lenses are distinguished by different names, according to the nature of their surfaces. Fig. 8.—Converging and Diverging Lenses. Lenses with sharp edges (thicker at the centre) are convergent or positive lenses. Lenses with blunt edges (thinner at the centre) are divergent or negative lenses. The first group comprises:—(1) The bi-

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Concave Lenses.

Concave Lenses.

The refracting influence of a concave lens ( Fig. 14 ) will be precisely the opposite of that of a convex. Rays which fall upon it in a parallel direction will be made to diverge as if from the principal focus, which is here called the negative focus. This will be, for a plano-concave lens, at the distance of the diameter of the sphere of curvature; and for a double-concave , in the centre of that sphere. Fig. 14.—A Virtual Image formed by Concave Lens. In Fig. 14 A B is the object and a b the i

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The Human Eye.

The Human Eye.

To gain a clear insight into the mode in which a single lens serves to magnify objects, it will be necessary to revert to the phenomena of ordinary vision. An eye free from any defect has a considerable power of adjusting itself to very considerable distances. One of the special functions of the eye is bringing the rays of light, by a series of dioptric mechanisms, to a perfect focus on its nervous sensitive layer, the retina. The eye in this respect has been compared to a photographic camera. B

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The Theory of Microscopical Vision.

The Theory of Microscopical Vision.

It has been said that no comparison can be instituted between microscopic vision and macroscopic; that the images formed by minute objects are not delineated microscopically under ordinary laws of diffraction, and that the results are dioptrical. This assertion, however, cannot be accepted unconditionally, as will be seen on more careful examination of the late Professor Abbe’s masterly exposition of “The Microscopical Theory of Vision,” and also his subsequent investigations on the estimation o

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Lord Rayleigh’s Theory of the Formation of Optical Images, with Special Reference to the Microscope.12

Lord Rayleigh’s Theory of the Formation of Optical Images, with Special Reference to the Microscope.12

Of the two methods adopted, that of Helmholtz’s consists in tracing the image representative of a mathematical point in the object, the point being regarded as self-luminous; that of Abbe’s the typical object was not, as we have seen, a luminous point , but a grating illuminated by plane waves of light. In the latter method, Lord Rayleigh argues that the complete representation of the object requires the co-operation of all the spectra which are focussed in the principal focal plane of the objec

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Definition of Aperture; Principles of Microscopic Vision.

Definition of Aperture; Principles of Microscopic Vision.

It must be well within the last half-century that the achromatic objective-glass for the microscope was brought to perfection and its value became generally recognised. Prior to the discovery of the achromatic principle in the construction of lenses it was assumed that the formation of the microscopic image took place (as we have already seen) on ordinary dioptric principles. As the image is formed in the camera or telescope, so it was said to be in the microscope. This belief existed, it will b

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Numerical Aperture.

Numerical Aperture.

Measure of Apertures of Objectives. N.A. —Numerical aperture, as it is termed, is measured by the scale of measurement calculated by the late Professor Abbe, and which has since been generally recognised and adopted. He showed that even in lenses made for the same medium (as air) their comparative aperture as compared with their focus was not correctly measured by the angle of the rays grasped, but by the actual diameters of the pencil of rays transmitted, which depend, as already seen, more upo

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Abbe’s Apertometer.

Abbe’s Apertometer.

Fig. 39.—Abbe’s Apertometer. The apertometer is an auxiliary piece of apparatus invented by Abbe, for testing the fundamental properties of objectives and determining their numerical and angular apertures. This accessory of the microscope involves the same principles as that of Tolles, which the late Mr. J. Mayall and myself brought to the notice of the Royal Microscopical Society of London in 1876. Abbe’s apertometer ( Fig. 39 ) consists of a flat cylinder of glass, about three inches in diamet

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Stereoscopic Binocular Vision.

Stereoscopic Binocular Vision.

Professor Wheatstone’s remarkable discovery of stereoscopic vision led, at no distant period, to the application of the principle to the microscope. It may therefore prove of interest to inquire how stereoscopic binocular vision is brought about. Indeed, the curious results obtained in the stereoscope cannot be well understood without a previous knowledge of the fundamental optical principles involved in this contrivance, whereby two slightly dissimilar pictures of any object become fused into o

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Simple and Compound Microscope.

Simple and Compound Microscope.

Microscopes are known as simple and compound. The simple microscope may, for convenience, be divided into two classes; those used in the hand (hand magnifiers), and those provided with a stand (mounted, as it is termed) for supporting the object to be viewed, together with an adjustment for the magnifying power, and a mirror for reflecting the light through the object. Fig. 47.—Visual Angle. A simple microscope , mounted, is preferable to a single lens, being usually composed of two or more lens

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The Compound Microscope.

The Compound Microscope.

The compound microscope differs from the simple, inasmuch as the image is formed by an object-glass, and further magnified by one or more lenses forming an eye-glass. For a microscope to be a compound one, its essential qualification is that it should have an object-glass or objective, and an eye-glass or eye-piece, so called because they are respectively near the object and the eye of the observer when the instrument is in use. The microscope consists of a tube or body , and a stand , an arrang

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Evolution of the Modern Achromatic Microscope.

Evolution of the Modern Achromatic Microscope.

The great advances made in the optical arrangements of the modern microscope necessitated important changes and improvements in its several mechanical parts. Indeed, as the apertures of objectives became increased, and focal planes became correspondingly shallower, it was absolutely necessary to apply a more sensitive system of focussing than that for many years past commonly in use. The leading manufacturers at once grasped the situation, and in a short space of time the older model microscopes

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Ross’s Microscopes.

Ross’s Microscopes.

Messrs. Ross have more recently introduced several changes and modifications in the Zentmayer stand, all tending to improve it, so that the Ross-Zentmayer model takes its place as a first-class microscope. Messrs. Ross have lately manufactured other forms of microscopes; one especially designed for those commencing the study of bacteriology ( Fig. 59 ). This instrument is one of the steadiest among those lately constructed for high-class work. The circular foot and short stout pillar support the

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Messrs. Beck’s Microscopes.

Messrs. Beck’s Microscopes.

Messrs. Beck have adopted what may be termed a rival system of fine adjustment in their modern microscopes. The short lever and screw applied externally to the body tube is peculiar, I may say, to the Ross-Jackson system, and was originally devised to allow of the body tube being supported somewhat more firmly on the limb. This change had its merits fully realised in the early microscopes of Smith and Beck. To their successors, R. &amp; J. Beck, the microscope owes much, and very many import

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Messrs. Watson’s Microscopes.

Messrs. Watson’s Microscopes.

Among London opticians, the various microscopes manufactured by Messrs. Watson, of Holborn, are of high finish and good workmanship. Those specially designed for the use of students possess merits of their own in their mechanical construction, and also embody a provision, as indeed do all their instruments, whether for students or more pretentious work, whereby wear and tear in their frictional parts can be compensated for by the user himself. This is effected in a simple but efficient manner. T

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Watson’s Mechanical Draw-tube.

Watson’s Mechanical Draw-tube.

Fig. 73.—Watson’s Mechanical Draw-tube (full-size). An important feature in connection with the body-tube of Watson’s Edinburgh Students’ Microscope (as, indeed, in all their fully furnished instruments) is that they are provided with two draw-tubes; one moved by rack-work, the other sliding inside the body-tube. The advantage is, that the body can be made very short or extremely long, while sufficient latitude can be given to objectives corrected for either Continental or English tube-lengths,

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Messrs. Swift’s Microscopes.

Messrs. Swift’s Microscopes.

Messrs. Swift’s Microscopes have a well-established reputation for quality and good workmanship, and therefore can in no way suffer by comparison when placed beside those of other opticians. One of the characteristics of Messrs. Swift’s microscopes—and this runs through the whole series—is that they are all made to a standard gauge, so that the several parts of the instruments, as well as their accessories, are interchangeable; the cheaper forms, with those of the first quality and finish. Shoul

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Messrs. Baker’s Microscopes.

Messrs. Baker’s Microscopes.

Of Messrs. Baker’s larger stands, the Improved “Nelson Model,” No. 2 ( Fig. 88 ) stand is selected in preference to their more elaborate No. 1, and their simpler form, No. 3, as a high-class instrument, and one well suited for fine critical work; the former being somewhat better, only from having extra adjustments; the latter possessing no superior advantage over the “Advanced Students’” Microscope. This microscope is mounted on a solid tripod foot, which insures stability, whether placed in a v

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Pillischer’s Microscopes.

Pillischer’s Microscopes.

Mr. Pillischer (New Bond Street) is favourably known for the excellency of his instruments. He has lately brought out several microscopes of an improved form. His larger model, the “New International,” consists of a solid, well-built, firm tripod stand of the Ross-Jackson pattern, which appears to be quite in the ascendant among London opticians; rack and pinion coarse adjustment, and a superior micrometer fine adjustment; sub-stage with centring screws and rack and pinion focussing adjustment;

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Continental Microscopes.

Continental Microscopes.

Continental Microscopes. —The better known among continental opticians are Zeiss, Leitz, Seibert, Reichert and Hartnack. All seem to have vied with each other in the attainment of perfection in the manufacture of the most useful forms of microscopes. The late Carl Zeiss did more for the modern microscope than either of the opticians referred to above. I therefore take a medium typical model of his from a long series of highly-finished instruments for my illustration. Zeiss’s successors have of l

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The Bacteriological Microscope.

The Bacteriological Microscope.

The microscope required for bacteriological studies should be perfect in all its parts. With regard to the choice of an instrument, it is very much a matter of price, since the most perfect is usually the most costly; I shall therefore proceed to give a typical example of the instrument in use in a bacteriological laboratory. The microscope should possess the following qualifications, all of which are absolutely necessary for the study of such minute objects as bacteria and other micro-organisms

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Applied Optics:—Eye-pieces; Achromatic Objectives; Condensers.

Applied Optics:—Eye-pieces; Achromatic Objectives; Condensers.

It is almost unnecessary to say that the eye-piece forms a most important part of applied optics in the microscope. It is an optical combination designed to bring the pencil of rays from the objective to assist in the formation of a real or virtual image before it arrives at the eye of the observer. Greater attention has been given of late years to the improvement of the eye-piece, since flatness of field much depends upon it. Opticians have therefore sought to make it both achromatic and compen

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The Achromatic Objective.

The Achromatic Objective.

Fig. 110.—Pan-aplanatic Achromatic Objectives. The Achromatic Objective , of all the optical and mechanical adjuncts to the microscope, is in every way the most necessary, as well as the most important. The ideal of perfection aimed at by the optician is a combination of lenses that shall produce a perfect image—that is, one absolutely perfect in definition and almost free from colour. The method resorted to for the elimination of spherical and chromatic aberration in the lens has been fully exp

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Relative Merits of the English and German Objectives.

Relative Merits of the English and German Objectives.

As to the relative merits of German-made objectives, no superiority can be claimed for them over those made by English opticians. The Continental form of the 1 ⁄ 12 -inch oil-immersion objective, shown in Fig. 118 , on the scale of 6 to 1, consists of four systems of lenses, namely, the front, a deep hemispherical crown lens of high refractive index; the second front of the system, an achromatic lens of such a form that it gathers the light from the hemispherical front; the middle lens, a single

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Abbe’s Test-plate.

Abbe’s Test-plate.

Abbe designed the test-plate ( Fig. 120 ) for testing the spherical and chromatic aberrations of objectives, and estimating the thickness of cover-glasses corresponding to the most perfect correction: six glasses, having the exact thickness marked on each, 0·09 to 0·24 mm., cemented in succession on a slip, their lower surface silvered and engraved with parallel lines, the contours of which form the test. These being coarsely ruled are easily resolved by the lowest powers; yet, from the extreme

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COVER-GLASS GAUGE.

COVER-GLASS GAUGE.

Zeiss has gone a step further to lay the microscopist’s ghost of the cover-glass. He invented a measurer ( Fig. 121 ) whereby the precise determination of thickness of glass-covers can be obtained. This measurement is effected by a clip projecting from a circular box; the reading is given by an indicator moving over a divided circle on the lid of the box. The divisions seen cut round the circumference show 1 ⁄ 100 ths of a millimeter. This ingenious gauge measures upwards of 5 mm. This necessary

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English Immersion and Dry Objectives.

English Immersion and Dry Objectives.

The homogeneous immersion system met with its earliest as well as its staunchest advocates among English opticians. Among its more energetic supporters were Messrs. Powell and Lealand, who were the first to construct a 1 ⁄ 8 -inch immersion objective on a formula of their own, and which was found to resolve test-objects not before capable of resolution by their dry objectives. This encouraged them to make a 1 ⁄ 16 -inch, acquired by Dr. Woodward for the Army Medical Department, Washington, and s

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Compensating Eye-pieces for use with Apochromatic Objectives.

Compensating Eye-pieces for use with Apochromatic Objectives.

This may be taken as a typical set, further treated of among Eye-pieces....

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Initial Powers of Objectives calculated for the 10-inch Tube-length.

Initial Powers of Objectives calculated for the 10-inch Tube-length.

This is ascertained by dividing the distance of distinct vision 10 inches by the focus of the objective, thus— A reference to the above table will at once show that the nomenclature of objectives expresses at once the initial magnifying powers, but as makers have great difficulty in so calculating their formulæ so as to obtain the exact power, these figures must be taken as approximate. Thus a ¼-inch, which should magnify 40 diameters if true to its description, might actually magnify a little m

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High-Power Objectives.

High-Power Objectives.

Points of Importance for securing the best results with High-power Objectives. —Always give to the body-tube of the microscope the length for which the objective is corrected, 0·160 mm. for the short continental tube, and 0·250 mm. for the English tube (10-inch). Employ both dry and immersion objectives mounted for correction, commencing with a numerical aperture of 0·75 (that is about 100° in air). If the graduation is not given in thickness of cover-glass apply to the maker to correct this omi

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Achromatic Condensers.

Achromatic Condensers.

The Achromatic Condenser can no longer be classed among the accessories of the microscope, since it is an absolutely indispensable part of its optical arrangements. Its value, then, cannot be overrated, and the corrections of the lenses which enter into the construction of the condenser should be made as perfect as they can be made—in fact, as nearly approaching that of the objective as it is possible to make them. It may therefore be of interest to know something of the rise and progress of the

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Abbe’s Condenser.

Abbe’s Condenser.

The essential feature of this condenser is its short focus, which collects the light reflected by the mirror, so as to form a cone of rays of very large aperture, having its focus in the plane of the object. Fig. 128.—The Iris Diaphragm, and carrier for Stops. The full aperture of the illuminating cone should only be used when finely granular and deeply stained particles (protoplasm, bacteria, &amp;c.) are being examined with objectives of large aperture. In all cases the cone must be suitab

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Oblique Illumination.

Oblique Illumination.

Wenham’s Parabolic Condenser. —Mr. Wenham’s many useful additions to the microscope and its accessories demand especial notice. When mention is made of the various immersion condensers (illuminators, as he preferred to call them), his original right-angled prism, his truncated hemispherical lens, his immersion paraboloid, and his reflex illuminator, in which rays beyond the angle of total reflexion are utilised by reflex action from cover-glass on to the surface of the object, every one of these

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Method of Employing the Achromatic Condenser to the Greatest Advantage.

Method of Employing the Achromatic Condenser to the Greatest Advantage.

Its Illumination. —Good daylight is the best for general work. The microscope should be placed near a window with a northern aspect. Direct sunlight should never be utilised; the best light is that reflected from a white cloud. A good paraffin lamp is the most serviceable artificial source of light, and it is quite under control. As an illuminant more often brought into requisition in the smoky atmosphere of towns, the paraffin lamp is on the whole the handiest and the most useful. If gas-light

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THE DIAPHRAGM.

THE DIAPHRAGM.

Fig. 150.—The Diaphragm. The early form of diaphragm in use was that shown in Fig. 150 . Fig. 151.—Shutter Diaphragm. It consists simply of a circular brass plate with a series of circular openings of different sizes, arranged to revolve upon another plate by a central pin or axis, the last being also provided with an opening as large as the largest in the diaphragm-plate, and corresponding in situation to the axis of the microscope body. The holes in the diaphragm-plate are centred and retained

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The Mirror.

The Mirror.

The mode in which an object is illuminated is, in the words of the late Andrew Ross, “second only in importance to the excellence of the glass through which it is seen.” To ensure good illumination the mirror should be in direct co-ordination with the objective and eye-piece; it must be regarded as a part of the same system, and tending by a combined series of acts to a perfect result. Illumination of the object is recognised as of three kinds or qualities—reflected, transmitted, and refracted l

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Accessories of the Microscope.

Accessories of the Microscope.

The accessories and appliances of the microscope have become so very numerous, that any attempt to describe them and explain the uses to which they are put would demand more space than I find myself in a position to bestow upon them. I must therefore confine my remarks to those accessories in more general use. Fig. 154.—The Lieberkühn. Having described the method of employing transmitted light, I have a few words to add with regard to the illumination of opaque objects by reflected light. A very

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The Bull’s-eye Condensing Lens.

The Bull’s-eye Condensing Lens.

This accessory is brought into constant use for the purpose of converging rays from a lamp or mirror; or, for reducing the diverging rays of the lamp to parallelism with the parabolic illuminator, or silver side-reflector. The form in use is a plano-convex lens of about three or four inches in focal length ( Fig. 159 ). It is usually mounted on a brass stand, so that it may be placed and turned in any direction, and at any height. When used by daylight, its plane side should be turned towards th

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Nose-pieces and Objective Changers.

Nose-pieces and Objective Changers.

A convenient appendage to the microscope is the rotating nose-piece, invented by Mr. Charles Brooke, F.R.S., and intended to carry two or more objectives, whereby a saving of time is effected, and the trouble of repeatedly screwing and unscrewing is avoided. In the application of the nose-piece attention should be given to centring. Messrs. Baker’s objective changer is intended to facilitate the placing and replacing the nose-piece in position. This adaptation consists of a milled head, acting o

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Micro-Photography.

Micro-Photography.

Micro-photography or photo-micrography, as it is indifferently termed, has, to a very considerable extent, superseded the use of the camera lucida for the delineation of images seen under the microscope. I may claim to be among the first workers with the microscope (1841) to prove beyond a doubt that the camera could be made to render invaluable aid to the microscopist, whereby a great saving of time might be effected, and a drawing obtained with greater accuracy than that of the pencil of the d

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Apparatus and Material.

Apparatus and Material.

Apparatus and Material used in micro-photography have, from time to time, been greatly varied by different workers, some preferring to use the microscope in the vertical position with the camera superimposed or fitted on the eye-piece of the microscope tube; others, again, prefer that both the microscope and the camera should be arrayed horizontally. In another form the ordinary microscope is dispensed with and the objective stage and mirror are adapted to the front of the camera, together with

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Polarisation of Light.

Polarisation of Light.

Common light moves in two planes at right angles to each other, while polarised light moves in one plane only. Common light may be turned into polarised light either by transmission or reflection; in the first instance, one of the planes of common light is got rid of by reflection; in the other, by absorption. Huyghens was one of the first physicists to notice that a ray of light has not the same properties in every part of its circumference, and he compared it to a magnet or a collection of mag

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Rotation of Plane of Polarisation.

Rotation of Plane of Polarisation.

When a plate of quartz (rock-crystal), even of considerable thickness, cut perpendicular to the axis, is interposed between the polariser and analyser, colour is exhibited, the tints changing as the analyser is rotated; and similar effects of colour are produced by employing, instead of quartz, a solution of sugar enclosed in a tube with plain glass ends. The action thus exerted by quartz and sugar is called rotation of the plane of polarisation , a name which sufficiently expresses the observed

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Molecular Rotation.

Molecular Rotation.

For the purpose of studying the various interesting phenomena of molecular rotation, a few necessary pieces of apparatus must be added to the microscope. First, an ordinary iron three-armed retort stand, to the lower arm of which must be attached either a polarising prism or a bundle of glass plates inclined at the polarising angle; in the upper an analysing prism. The fluid to be examined should be contained in a narrow glass tube about eight inches in height, and this must be attached to the m

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Formation and Polarisation of Crystals.

Formation and Polarisation of Crystals.

The inorganic kingdom will afford to the microscopist a never-ending number of objects of unsurpassed beauty and interest. The phenomena of crystallisation in its varied combinations can be made a useful and instructive occupation. Although ignorant of the means whereby the great majority of minerals and crystals have been formed in the vast laboratory of Nature, we can, nevertheless, imitate in a small degree Nature’s handiworks by crystallising out a large number of substances, and watch their

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SALTS.

SALTS.

Alum. Asparagine. Aspartic Acid. Plate VIII . No. 168. Bitartrate of Ammonia. Boracic Acid. Borax. No. 164. Carbonate of Lime. " Soda. Chlorate of Potash. Chloride of Barium. " Cobalt. " Copper and Ammonia. " Sodium. Cholesterine. Chromate of Potash. Cinchonine. Cinchonidine. Citric Acid. Hippuric Acid. Iodide of Mercury. " Potassium. " Quinine. Iodo-disulphate of Quinine. Kreatine. No. 166. Murexide. Nitrate of Bismuth. " Barytes. " Brucine. " Copper. " Potash. " Strontian. " Uranium. Oxalate o

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MINERALS.

MINERALS.

Agates, various. Asbestiform Serpentine. Avanturine. Carbonate of Lime. Carrara Marble....

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ANIMAL STRUCTURES.

ANIMAL STRUCTURES.

Cat’s Tongue. No. 174. Grayling Scale. No. 176. Holothuria, Spicules of. Nos. 171-2. Prawn Shell. No. 175....

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VEGETABLE CRYSTALLINE SUBSTANCES.

VEGETABLE CRYSTALLINE SUBSTANCES.

Cuticle of Leaf of Correa Cardinalis. " " Deutzia scabra. No. 173. " " Elæagnus. " " Onosma taurica. Equisetum. No. 170. Fibro cells from orchid. No. 169. " Oncidium bicallosum. Scalariform Vessels from Fern. Scyllium Caniculum. No. 177. Silicious Cuticles , various. Starches, various. No. 167. The formation of artificial crystal may be readily effected, and the process watched, under the microscope, by simply placing a drop of saturated solution of any salt upon a previously warmed slip of glas

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The Micro-spectroscope.

The Micro-spectroscope.

Spectrum analysis has, from its first introduction by Kirschoff in 1859, maintained its fascination over men of science throughout the civilised world. Microscopists, astronomers, and chemists have assigned to the spectroscope a highly important position amongst scientific instruments of research. At quite an early period of its history it appeared to ourselves to promise an extension of the work of the microscope in pathology and microscopy, and second only to that of astronomy and chemistry. T

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Method of using the Micro-Spectroscope.

Method of using the Micro-Spectroscope.

A beginner with the micro-spectroscope should first make himself fully acquainted with the spectroscope by holding it up to the sky and noting the effects of opening and regulating the slit, by rotating the screw C , Figs. 195 and 197. The lines will be well seen on closing down the opening. This screw diminishes the length of the slit, when the spectrum is seen as a narrow ribbon of prismatic colours. The screw E regulates the admission of light through the aperture above D . The better objects

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Absorption Spectrum of Chromule.

Absorption Spectrum of Chromule.

In 1869 I published in the Journal of the Royal Microscopical Society 38 a paper on results obtained by the spectrum analysis of the colouring-matter of plants and flowers, some of which were of considerable interest in many respects. My examinations extended to several hundred different specimens, from which I was led to conclude that the chromule of flowers is, for the most part, due to the chemical action of the actinic rays of light over the protoplasm of the plant, more so than to that of s

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Practical Microscopy: Manipulation, and Mode of Using the Microscope.

Practical Microscopy: Manipulation, and Mode of Using the Microscope.

In this chapter it will be my aim to discuss the best practical methods of employing the microscope and its appliances to the greatest advantage. First, the student should select a quiet room for working in, with, if possible, a northern aspect, free from all tremor occasioned by passing vehicles. The table selected for use should be firm, and provided with drawers, in which his several appliances can be kept ready to hand. The microscope must be placed at such an inclination as will enable him

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Directions for finding the best Focus.

Directions for finding the best Focus.

The method of finding and determining when the screw-collar adjustment of the high-power objective has arrived at a point of perfect definition and magnification is as follows:— Select any dark speck of dust, or an opaque portion of the object, and carefully focus this small particle by working the screw of the fine adjustment, move the screw up and down until you are satisfied the image is the sharpest and blackest that can be obtained, then once more test the focus a little above and a little

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Working Accessories.

Working Accessories.

A glass plate with a ledge, and some pieces of thin glass , although applicable for many purposes, are specially designed for objects in fluid. Thus a drop of fluid containing the object sought for is placed upon the slide and covered by a piece of thin glass; or, the object being put upon the glass slide and the thin glass over it, the fluid is applied near one side, and runs under by capillary attraction. Fig. 208.—Varley’s Live-box. Troughs and Live-box. —These are made of various materials,

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Methods of Preparing, Hardening, Staining and Section Cutting.

Methods of Preparing, Hardening, Staining and Section Cutting.

Numerous methods are employed for the preparation, hardening, staining, and section cutting of animal and vegetable tissues for the microscope, the details of which are modified, or varied as may be found needful, from time to time, by those whose intimate acquaintance with the subject entitles them to make innovations and changes in this very important department of microscopy. In the hands of the original worker, formulæ and methods will only be regarded as finger-posts pointing out a means of

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Staining Animal Structures.

Staining Animal Structures.

Specific stains are chiefly employed to assist the eye in distinguishing one elementary tissue from another. It is therefore necessary to stain all structures, as certain parts are seen to have a special affinity for one colouring agent rather than another, whereby they become more deeply stained, and consequently more clearly differentiated. For staining animal structures, borax, carmine, and hæmatoxylin are more frequently employed than others. The formulæ for each will be found in the Appendi

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Double and Treble Staining.

Double and Treble Staining.

Dr. W. Stirling 46 furnishes a brief but useful account of the methods he has employed with much success. Osmic Acid and Picro-carmine. —Mix on a glass slide a drop of the blood of newt or frog and a drop of a one per cent. aqueous solution of osmic acid, and allow the slide to stand by. This will fix the corpuscles without altering their shape. At the end of five minutes remove any excess of acid with blotting-paper, add a drop of a solution of picro-carmine, and a trace of glycerine to prevent

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Injecting Small Animal Bodies.

Injecting Small Animal Bodies.

Fig. 241.—Injecting Syringe. Fig. 242.—Water Bath and Melting Vessels. The injection of animal bodies practised by the older anatomists, to render the vascular system more apparent, has not been superseded by the more modern methods of staining. The method of injecting even small bodies requires some skill, and a few pieces of apparatus made expressly for the purpose. First, a special form of brass syringe of such a size that it may be grasped with the right hand, the thumb at the same time cove

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Cutting, Grinding, and Mounting Hard Structures.

Cutting, Grinding, and Mounting Hard Structures.

Take the femur of cat, or rabbit, remove as much of the muscle as possible and macerate it in water until quite clean; on removal hang it up to dry. With a fine saw make transverse and longitudinal sections. File the section down until flat, and smooth. Take some Canada balsam, place a piece on a square of glass and warm gently over a lamp until the balsam is plastic enough to allow of the section being pressed into it, and set it aside to consolidate. Take a hone (“Water-of-Ayr” stone), moisten

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Bacteria Cultivation, Sterilising, and Preparing for Microscopical Examination.

Bacteria Cultivation, Sterilising, and Preparing for Microscopical Examination.

That branch of mycology which is now looked upon as a separate department of science, termed bacteriology, took shape in the years 1875-9, when its founder, the veteran botanist Cohn, who recognised that the protoplasm of plants corresponded to the animal sarcode, published his exact mode of studying bacteria. But it was a pupil of his, Dr. Koch, who a year later discovered that a specific cattle disease, anthrax, was due to a bacillus, and it was he also who gave us the useful modification of g

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Apparatus, Material, and Reagents employed in Bacteriological Investigations.

Apparatus, Material, and Reagents employed in Bacteriological Investigations.

A good microscope with a wide-angled sub-stage condenser, and objectives of an inch, ¼-inch, or 1 ⁄ 6 -inch, and a 1 ⁄ 12 -inch homogeneous oil-immersion. A large bell-glass for covering the same when fuming acids are in use in the laboratory. About a square foot of blackened plate-glass. A white porcelain slab, or a shallow photographic dish of some size. Glass bottles with ground stoppers for alcoholic solutions and aniline dyes. Glass bottles with funnels for filtering solutions of stains, wi

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Apparatus for Incubation and Cultivations in Liquid Media.

Apparatus for Incubation and Cultivations in Liquid Media.

Lister’s Flasks. —Lister devised a globe-shaped flask with two necks, a vertical and a lateral one, the lateral being a bent spout, tapering towards the extremity. When the vessel is restored to the erect position after pouring out some of its contents, a drop of liquid remains behind in the end of the nozzle, and thus prevents the regurgitation of air through the spout. A cap of cotton-wool is tied over the orifice, and the residue left in the flask for future use. The vertical neck of the flas

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THE WARM CHAMBER, STERILISER, AND INCUBATOR.

THE WARM CHAMBER, STERILISER, AND INCUBATOR.

Fig. 256.—Pfeiffer’s Warm Chamber. The Warm Chamber. —This is an accessory of importance in bacteriological work. For the continuous heating of specimens during cultivation it is an absolute necessity. Pfeiffer’s warm chamber ( Fig. 256 ) is suitable for microscopical work generally. It consists of a hard-wood box, made air-tight, with doors and glass windows to allow of the specimen being moved from time to time, and kept under constant observation. The box is mounted on a metal plate tripod st

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Preparation of Nutrient Media—Separation, and Cultivation of Bacteria.

Preparation of Nutrient Media—Separation, and Cultivation of Bacteria.

Fig. 260.—Plate Cultivation Showing Colonies. To cultivate micro-organisms artificially they must be supplied with the proper nutrient material, perfectly free from pre-existing organisms. The secret of Koch’s methods greatly depends upon the possibility, in the case of starting with a mixture of micro-organisms, of being able to isolate them completely one from another, and to obtain an absolutely pure growth of each cultivable species. When sterile nutrient gelatine has been liquefied in a tes

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Microscopical Examination of Bacteria.

Microscopical Examination of Bacteria.

Bacteria in Liquids, Cultures, and Fresh Tissues. —In conducting bacteriological researches, the importance of absolute cleanliness cannot be too strongly insisted upon. All instruments, glass vessels, slides, and cover-glasses should be thoroughly cleansed before use. The same applies to the preparation and employment of culture media; any laxity in the processes of sterilisation, or insufficient attention to minute technical details, will be followed with disappointing results by contamination

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Staining of Flagella.

Staining of Flagella.

Koch first stained flagella by floating the cover-glass on a watery solution of hæmatoxylin, transferring them to a five per cent. solution of chromic acid, or to Müller’s fluid, by which they obtained a brownish-black coloration. Löffler’s Method. —Add together aqueous solutions of ferrous-sulphate and tannin (twenty per cent.) until the mixture turns a violet-black colour, then add three or four cc. of a one-in-eight aqueous solution of logwood; a few drops of carbolic acid may be added before

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Bacteria in Sections of Tissues.

Bacteria in Sections of Tissues.

Method of Hardening and Decalcifying Tissues. —To harden small organs, such as the viscera of a mouse, they should be placed on a piece of filter-paper at the bottom of a small wide-mouthed glass jar, and covered with about twenty times their volume of absolute alcohol. Larger organs are treated in the same way, but must be cut up into small pieces. Müller’s fluid, methylated spirit, or formalin may be used. Teeth, or osseous structures, must first be placed in a decalcifying solution, as Kleine

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Preparing, Mounting, Cementing and Collecting Objects.

Preparing, Mounting, Cementing and Collecting Objects.

Various materials are required for preparing and mounting microscopic objects, as slips of glass, patent flatted plate measuring 3 × 1 inch, thin glass covers, glass cells, preservative media, varnishes, cements, a glazier’s diamond, and a Shadbolt’s turn-table. The glass slides and covers, although sent out packed ready for use, should be immersed in an alkaline solution to ensure perfect freedom from any greasiness derived from touching by the fingers. Dr. Seller recommends a particular soluti

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Collection of Objects.

Collection of Objects.

Infusorial Life , with all its fascinations, was fully unveiled to naturalists by the celebrated Ehrenberg. It was he who termed it infusorial, because he first met with the more interesting forms of minute life in infusions of hay and other vegetable substances. Since his day it is a well-known experience of those who take up the microscope that the most interesting objects to commence with are infusorial living creatures of sufficient dimensions to be easily understood and seen with moderate m

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Microscopic Forms of Life—Thallophytes—Pteridophyta, Phanerogamæ—Structure and Properties of the Cell.

Microscopic Forms of Life—Thallophytes—Pteridophyta, Phanerogamæ—Structure and Properties of the Cell.

The time has long since passed by since the value of the microscope as an instrument of scientific research might have been called in question. By its aid the foundation of mycology has been securely laid, and cryptogamic botany in particular has, during the last quarter of a century, made surprising progress in the hands of those devoted to pursuits which confer benefits upon mankind. Little more than thirty years ago practically nothing was known of the life history of a fungus, nothing of par

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Pathogenic Fungi and Moulds.

Pathogenic Fungi and Moulds.

It is scarcely necessary to go back to the history of the parasitic fungi to which diseases of various kinds were early attributable. The rude microscopes of two and a half centuries ago revealed the simple fact that all decomposable substances swarmed with countless multitudes of organisms, invisible to ordinary vision. Leuwenhoek, the father of microscopy, and whose researches were generally known and accepted in 1675, tells of his discovery of extremely minute organisms in rain-water, in vege

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Parasitic Diseases of Plants.

Parasitic Diseases of Plants.

The subject of fungoid diseases and fungus epidemics are of worldwide interest, if only because of the annual losses to agriculturists from parasitic diseases of plants, amounting to millions of pounds sterling. The history of wheat-rust, and that of oats and rye, each equally susceptible to the ravages of the same Rufus, can be traced back to Genesis. A description of it was given in 1805 by Sir Joseph Banks. He suggested that the germs entered the stomata, and he warned farmers against the use

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Habitat of Fungi and Moulds.

Habitat of Fungi and Moulds.

Fig. 273.—Fungi and Moulds. Description of Figures.— a. Fungi Spores, taken in a sick chamber; b. Aspergillus glaucus ; c. Yeast, recent state; d. Exhausted yeast, budding; e. Penicillium spores more highly magnified; g. Aerobic spores and mould mycelium; h. Aspergillus spore, grown on melon....

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Habitat, Specialised Forms of Parasites.

Habitat, Specialised Forms of Parasites.

Habitat. —The habitat of vegetable parasitic fungi is extremely variable. Fungi are found everywhere, living and flourishing on all the families of the vegetable and animal kingdoms. They attack our houses, foods, clothes, utensils of every kind, wall papers and books, the paste of which, to my astonishment, affords a sufficient supply of nourishment. Members of the parasitic tribe of bacteria, by a combined effort of countless myriads, have given rise to a sense of supernatural agency. Bacillus

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Parasitic Fungi of Men and Animals.

Parasitic Fungi of Men and Animals.

In the microscopical examinations especially given to the elucidation of parasitic diseases of the skin, previously referred to, I discovered more varieties of spores and filaments of certain cryptogamic plants associated with a larger number of specific forms of fungi than any previous observer. I did not, however, feel justified in concluding, with Küchenmeister, Schœnlein, and Robin, that these fungoid growths were the primary cause of the diseases referred to. Indeed, the foremost dermatolog

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Industrial uses of Fungi and Saccharomycetes.

Industrial uses of Fungi and Saccharomycetes.

There are many industrial processes which are more or less dependent for success on bacterial fermentations. The subject is young, but the results already obtained are seen to be of immense importance from a scientific point of view, and to open up vistas of practical application already being taken advantage of in commerce, while problems are continually being raised by the forester, the agriculturist, the gardener, the dairyman, the brewer, dyer, tanner, and with regard to various industries,

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Results of De Bary’s Investigations in Parasitism.

Results of De Bary’s Investigations in Parasitism.

“When the idea of parasitism was rendered definite by the fundamental distinction drawn by De Bary between a parasite and a saprophyte , it soon became evident that some further distinction must be made between obligate facultative parasites and saprophytes respectively. De Bary, when he proposed these terms for adoption, was clearly alive to the existence of transitions which we now know to be numerous and so gradual in character that we can no longer define any such physiological groups. Twent

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Desmidiaceæ and Diatomaceæ.

Desmidiaceæ and Diatomaceæ.

The two groups of Desmidiaceæ and Diatomaceæ differ so little in their general characters that they may be spoken of as members or representative families of microscopic and unicellular algæ alike in their remarkable beauty and bilateral symmetry, and of such peculiar interest as to call for special notice. Desmids differ from diatoms chiefly in colour, in lacking a non-silicious skeleton, and in their generative process, which for the most part consists in the conjugation of two similar cells.

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Movements of Diatoms.

Movements of Diatoms.

The late Professor Smith, in his “Synopsis of Diatoms,” refers to their movements in the following terms: “I am constrained to believe that the movements observed in the Diatomaceæ are due to forces operating within the frustule, and are probably connected with the endosmotic and exosmotic action of the cells. The fluids which are concerned in these actions must enter, and be emitted through the minute foramina at the extremities of the silicious valves.” Schultze’s researches, which were made a

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Diatomaceæ, Recent and Fossil.

Diatomaceæ, Recent and Fossil.

Fig. 298.—Fossil Diatoms from Springfield (Barbadoes). 1, Achnanthidium; 2, Diatoma vulgare , side view and front view; 3, Biddulphia; 4, 5, 6, 7, Amphitetias antediluviana , front view, with globular and oval forms; Gomphonema elongatum and capitatum . Fossilised Diatomaceæ. —Dr. Gregory was of opinion that a large number of diatoms separated into species are only transition forms, and more extended observations have proved that form and outline are not always to be trusted in this matter. Spec

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Lichenaceæ.

Lichenaceæ.

The lichens are a family of autonomous plants, an intermediary group of algals or cellular cryptogams, drawing their nourishment from the air through their whole surface medium, and propagating by spores usually enclosed in asci, and always having green gonidia in their thallus. Their gonidia, bright coloured globular cells, form layers under the cortical covering of the thallus, and generally develop in the form of incrustations, which cover stones, wood, and the bark of trees, or penetrate int

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Musci, Bryophyta.

Musci, Bryophyta.

Mosses are a beautiful class of non-vascular cryptogams. Linnæus called them servi , servants or workmen, as they seem to labour to produce vegetation in places where soil is not already formed. The Bryophyta form three natural divisions: the Bryinæ, or true mosses; the Sphagnaceæ, or peat-mosses; and the Hepaticæ, or liverworts. The two first are commonly united. In these the sexual organs consist of antheridia and archegonia, but they are of simpler structure than will be found in ferns; and t

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Structure of Phanerogamiæ or Flowering Plants.

Structure of Phanerogamiæ or Flowering Plants.

The two great divisions of the vegetable kingdom are known as Cryptogamia and Phanerogamia. It does not follow, however, that there is any abrupt break between the two, as will appear from the context. Although it is customary to speak of the flowering plants as a higher grade of life, yet there is an intermediary class of Phanerogamiæ in which the conspicuous parts of the generative system partake of a condition closely resembling those of the higher Cryptogamiæ, observed in Gymnosperms, Conife

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The Sub-kingdom Protozoa.

The Sub-kingdom Protozoa.

The consideration of the whole special group of organisms forming the subject matter of this chapter, under the heading of Protozoa, were formerly included among Infusoria, which also embraced every kind of microscopical aquatic body, whether belonging to the vegetable or animal series. A more critical survey of the organisation and affinities of Infusoria and the members which constituted the group led to a re-arrangement, which has been very generally accepted as forming a sub-kingdom, Protozo

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Infusoria.

Infusoria.

We are now brought face to face with animals which possess considerable variation of structure, Infusorial animalcules , as they are termed. It was Ehrenberg who attributed to them a highly complex organisation, but later observations negatived these views and showed them to be animals formed of one or more cells, or colonies of so-called individuals. It is true that this cell or united protoplasm may show a wonderful amount of differentiation, what with its nucleus and vacuole, mouth and gullet

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Porifera. Spongiadæ.

Porifera. Spongiadæ.

Fig. 340.— Spongia panicea. Bread-crumb Sponge, showing currents entering surface a , and leaving by oscules b . Sponges. —The term Porifera, or “canal-bearing zoophytes,” was applied by the late Dr. Grant to designate the remarkable class of organisms known as sponges, met with in every sea, and numbering about two thousand species, varying in size from a pin’s head to masses several feet in height; and weighing from a few grains to over a hundred pounds. Sponges assume an endless variety of sh

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Zoophytes, Cœlenterata, Medusæ, Corals, Hydrozoa.

Zoophytes, Cœlenterata, Medusæ, Corals, Hydrozoa.

Fig. 344.—Gorgonia Nobilis. A study of the earliest growth of the Cœlenterata has shown that their internal cavities are nothing more than regular radiate out-growths of the internal structures. The result of this development is a condition which does not occur again in the whole of the animal kingdom. There is a system of cavities all in open communication one with another, no closed blood vascular system, and no specialised respiratory apparatus. Again, all the animals that constitute this lar

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Bryozoa, Moss-animals.

Bryozoa, Moss-animals.

The exact position in which the Bryozoa, or moss-animals, should be placed in the animal kingdom has not been finally determined. They were at one time associated with corals; then with sponges; but, on further acquaintance, it became evident that they did not belong to either. Naturalists also claimed them as Rotifers and Ciliata, but this claim met with no better reception. Since they appear to have no settled classification, there can be no objection to linking them once more to corals, as th

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Annulosa, Worms, and Entozoa.

Annulosa, Worms, and Entozoa.

The Annulosa of Huxley embraces the lowest grade of articulated animals, most of which are now grouped with Metazoa, while some writers place them in a sub-kingdom Vermes. It appears to me then only possible to describe this heterogeneous group of worm-like animals among those which resemble each other in certain negative features, but not possessing any of the distinctive characters of those previously described. There are numerous species among Entozoa, every one of which is of the highest int

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Crustacea.

Crustacea.

The crustaceans comprise a large assemblage of Arthropods, presenting great diversity of structure. Some of the parasitic species have become so simplified in organisation that they appear to present no relationship with the higher members of the class, yet it is certain that all the species, whether terrestrial or aquatic, belong to the same stock, and may have had origin in the same fundamental plan of structure. Essentially, the body consists of a large number of segments, to each of which is

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Arthropoda—Insecta.

Arthropoda—Insecta.

Distinctive Characters of Insects. —The term Insect, although originally and according to the meaning of the word correctly employed in a wide sense to embrace all those articulate creatures in which the body is externally divided into a number of segments, including, of course, flies, butterflies, beetles, bugs, spiders, scorpions, crabs, shrimps, &amp;c., is now by common consent used in a much more restricted sense to apply only to such of these animals as have six walking legs. Insects b

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Vertebrata.

Vertebrata.

The most complicated condition in which matter exists is where, under the influence of life, it forms bodies with a structure of tubes and cavities in which fluids are incessantly in motion, and producing continuous changes. These have been rightly designated “organised bodies,” because of the various organs they contain. The two principal classes into which organised bodies have been divided are recognised as vegetable and animal. It was Bichat who taught that our animal life is double, while o

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The Mineral and Geological Kingdoms.

The Mineral and Geological Kingdoms.

The structure of rocks and the formation of crystals will be found to furnish an endless supply of instructive material for the microscope. In sciences of pure observation, as those of mineralogy and geology, the facts to be observed are of several different kinds, and where so many observers are at work all over the world, constant progress will necessarily be made, as well as continued correction required from change and improvement in the methods of observation. It would be impossible to give

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Appendix A.

Appendix A.

A doubt has of late been expressed among practical microscopists as to the value of the illumination arrangements of the lamp and the microscope, so as to secure the more perfect definition of the flagellate organ of the monas and other minute forms of infusorial life. We have been told that better results will be obtained by turning the mirror aside, and so disposing the microscope and lamp in the horizontal position, that the central rays of light from the mirror-edge of the lamp-flame shall p

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Appendix B.

Appendix B.

Owing in some measure to the more complete knowledge of the subject gained by the experience of years, and the extreme value of micro-photography in the delineation of bacteria, and perhaps in a measure to the advent of the perfected dry-plate process, photography is being rapidly pressed forward in conjunction with the microscope. In the course of the year [1898] no less than six, more or less, new forms of micro-photographic apparatus have appeared; two are simple, one for daylight, one for la

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Appendix C.

Appendix C.

FORMULÆ AND METHODS:—CEMENTING, CLEARING, HARDENING AND MOUNTING. 90 The object of employing a clearing agent is to replace the alcohol in the dehydrated section by a liquid which has a refractive index about the same as the balsam into which it is to be placed, and which will readily mix with it. Oil of Bergamot will clear quickly from 90 per cent. of alcohol. Clove oil clears more rapidly, but it dissolves out aniline colours to a considerable extent. Xylol is without action on aniline colours

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Appendix D.

Appendix D.

The initial unit of the Metric System is the Metre or unit of length, which represents one ten millionth part of the earth’s quadrant, or one forty-millionth part of the circumference of the earth around the poles. The multiples and sub-divisions of this and all the other units are obtained by the use of decimals, and for this reason the system is also known as the decimal system . The multiples are designated by the Greek prefixes, deca = 10; hecto = 100; kilo = 1000; myria = 10,000. For the su

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Appendix E.

Appendix E.

Dr. Culpeper’s Microscope 1738....

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