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PREFACE
PREFACE
My introductory treatise on the Entozoa having long been out of print, it occurred to me that instead of attempting another edition it would be better to write an entirely new work, employing only such fragmentary portions of the old treatise as would harmonise with the far wider design I have now in view. Whilst, therefore, I have freely utilised a selection of the illustrations given in the elementary volume, comparatively few of its pages have been incorporated in the present work. Dealing wi
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ERRATUM.
ERRATUM.
Page 296 , line 24 from the top, for “in the glow-worm ( Glomeris ),” read “in a myriapod ( Glomeris ) which is phosphorescent like the glow-worm.”...
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INTRODUCTION.
INTRODUCTION.
No person can derive advantage from the study of parasites unless the subject be approached in a right frame of mind. In other words, the student of helminthology must, as a primary discipline, dispossess himself of all preconceived opinions whatsoever, and in an attitude of child-like simplicity seek truth for its own sake. Unless the mind be absolutely free and unfettered it cannot rightly interpret the facts of this peculiar department of biological science. Those students who are nervously a
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PARASITES OF MAN.
PARASITES OF MAN.
Whatever notions people may entertain respecting the dignity of the human race, there is no gainsaying the fact that we share with the lower animals the rather humiliating privilege and prerogative of entertaining a great variety of parasites. These are for the most part entozoal in habit. As the parasites are apt to cause suffering to the bearer, a superstitious age sought to interpret their presence as having some connection with human wrong-doing. We can now afford to smile at such erroneous
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SECTION I.—Trematoda (Flukes).
SECTION I.—Trematoda (Flukes).
Fasciola hepatica , Linneus.—The first form I have to consider is the common liver fluke. The part this entozoon plays in the production of disease will be fully stated when treating of the parasites of the sheep and other ruminants. About twenty instances of its occurrence in the human body have been recorded. It has been found beneath the skin in the sole of the foot (Giesker), and also under the scalp (Harris), and behind the ear (Fox). Its more frequent seat is in the liver and gall-ducts (P
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SECTION II.—Cestoda (Tapeworms).
SECTION II.—Cestoda (Tapeworms).
Tænia mediocanellata , Küchenmeister.—This cestode is frequently spoken of as the unarmed or beef tapeworm. In general appearance it is very similar to the armed form. It is, however, a larger and broader animal, being at the same time rather stouter. It varies usually from fifteen to twenty-three feet in length, but specimens have been described as attaining thirty feet. It is called the unarmed tapeworm in consequence of the absence of any coronet of hooks on the head; and consequently, also,
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SECTION III.—Nematoda (Round Worms).
SECTION III.—Nematoda (Round Worms).
Trichina spiralis , Owen.—The progressive triumphs of biological science are well epitomised in the history of the discovery, and in the record of the gradual manner in which we have obtained our present complete knowledge of the structure and development of this small entozoon. Although the facts connected with the original discovery are clear and indisputable, much error still pervades foreign literature on this head. Without a doubt Mr Hilton was the first to suggest the parasitic nature of t
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SECTION IV.—Part I.—Acanthocephala (Thornheaded worms).
SECTION IV.—Part I.—Acanthocephala (Thornheaded worms).
Echinorhynchus gigas , Goeze.—There is but one recorded instance of the occurrence of this entozoon in the human body. This is the oft-quoted case by Lambl, given in the ‘Prager Vierteljahrschrift’ for 1859. Lambl, indeed, described it as a separate species ( E. hominis ), but as the worm was a sexually-immature female, its identification with E. gigas , notwithstanding Schneider’s great authority, can hardly be regarded as absolutely certain. The worm was found in the small intestine of a boy o
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SECTION IV.—Part II.—Suctoria (Leeches)
SECTION IV.—Part II.—Suctoria (Leeches)
As explained in the Introduction we must regard the Leeches and many allied forms of Suctorial Annelids as creatures possessed of semi-parasitic habits. They are, perhaps, something more than what Van Beneden styles “free parasites”—an expression which almost looks like a contradiction of terms. I cannot here, however, stop to discuss questions which lie, as it were, on the border-land of parasitology. Three species of leech are more or less commonly employed in medicine. These are the grey leec
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SECTION IV.—Part III.—Arachnida (Pentastomes, Mites, Ticks).
SECTION IV.—Part III.—Arachnida (Pentastomes, Mites, Ticks).
The Trachearian division of the Arachnida comprises a few internal parasites that attack man, and many ectozoa which are parasitic upon man and animals. The species can only be noticed very briefly. Pentastoma tænioides , Rudolphi.—In the system of classification adopted by Diesing, this entozoon and its allies are placed in the division Cephalocotyleen and therefore, in association with the Cestodes, with which, however, it has no structural affinity. It was long ago pointed out by Van Beneden,
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SECTION IV.—Part IV.—Crustacea (Gammaridæ).
SECTION IV.—Part IV.—Crustacea (Gammaridæ).
Although multitudes of small Crustaceans are parasitic upon fishes, and some few of them adhere to oceanic mammals (Cetacea), I am sceptical as to the parasitism of Crustacea either in or upon man. Many of the Amphipodous Gammari lead a sort of free parasitic existence, and they are themselves very liable to harbor larval parasites. As regards human parasitism from this source the only records known to me are those quoted below. Bibliography ( No. 39).— Banon , “Freshwater Shrimp, or Gamarus pul
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SECTION IV.—Part V.—Insecta (Coleoptera, Diptera, Hemiptera, Aphaniptera).
SECTION IV.—Part V.—Insecta (Coleoptera, Diptera, Hemiptera, Aphaniptera).
Whilst very many flies, bugs, lice, and fleas persecute animals, not a few of them also attack man. Several of the species are genuine parasites, others are semi-parasitic, and others, again, are altogether outside the border-land of parasitism in the ordinary sense of the term. In fact, it becomes difficult to say where the line of parasitism should be drawn. I cannot, however, ignore all notice of the insect tormentors, whether strictly parasitic or not. At least fifty different species have b
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SECTION IV.—Part VI.—Protozoa (Psorospermiæ, Gregarinidæ, &c.).
SECTION IV.—Part VI.—Protozoa (Psorospermiæ, Gregarinidæ, &c.).
The scope of this work does not demand that I should comprise within its limits any vegetable parasites; nevertheless, I must needs refer, however briefly, to certain confervoid and sarcodic organisms, which, for the most part, lie on the borderland of the animal and vegetable kingdoms. Professor Cohn regards the bacteria as allied to the Oscillitoriaceæ. He puts them in his order Schizosporeæ . It is of little moment, practically, where these protista forms are placed. Unquestionably many of th
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PARASITES OF ANIMALS.
PARASITES OF ANIMALS.
In dealing with this division of the subject it will be impossible to give more than the faintest outline. Let it be borne in mind that quite as much information might be offered by me respecting the parasitism of each of the commoner domestic animals as has been already advanced in regard to the helminthism of man. That would by no means exhaust the subject. Thus treated, a score of volumes, each equal in size to this, would barely suffice to cover the whole ground of Parasitology; and yet ther
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SECTION I (Mammalia).
SECTION I (Mammalia).
In dealing with this class of hosts, exclusive of man, I shall notice the entozoa of the various orders successively, taking the arrangement which I employed many years since when writing the Mammalian Division of a popular treatise called the ‘Museum of Natural History.’ The internal parasites of those orders which happen to embrace important domesticated animals will necessarily receive more attention than the others; some notice of the ectozoa being likewise added....
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Part I.—Quadrumana (Monkeys).
Part I.—Quadrumana (Monkeys).
Monkeys are less afflicted with flukes than most animals. The species known to me are Distoma laciniatum , found by Brongniart in the pancreas of Simia maimon ; D. orbiculare and Amphistoma emarginatum , from the intestines of Cebus trivirgatus ; and Bilharzia hæmatobia , a single specimen of which I obtained from Cercopithecus fuliginosus . The monkeys of the Old World rarely harbor full-grown tapeworms, but Cysticerci are abundant ( Cyst. tenuicollis , C. cellulosa , C. pileatus , C. crispus )
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Part II (Cheiroptera).
Part II (Cheiroptera).
Until lately not very much attention had been paid to the parasites of bats, probably on account of the insignificance of the hosts. However, whilst Dr Dobson has recently been extending the subject of Cheiropterology, Prof. van Beneden has added largely to our knowledge of the parasites of bats. In his beautiful memoir, the Belgian helminthologist asks whether the parasites quit their hosts during the period of hybernation, and then proceeds to answer that question in the negative. Should the b
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Part III (Insectivora).
Part III (Insectivora).
The entozoa of insectivorous mammals, though sufficiently numerous, are not important practically. The common hedgehog ( Erinaceus europæus ) is infested by four flukes ( Distoma pusillum , D. trigonocephalum , D. caudatum , D. linguæforme ), and also by three thorn-headed worms ( Echinorhynchus napæformis , E. amphipachus , and E. major ). Two tapeworms are also known ( Tænia compacta and T. tripunctata ). More attention has been paid to the round worms. A species of strongyle ( S. striatus ) i
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Part IV (Carnivora).
Part IV (Carnivora).
Notwithstanding the importance of the entozoa of this large section of mammals, I must deal with them very summarily, emphasising my remarks on the parasites of the dog and cat. Only a few of the ectozoa can be noticed. The bears are much infested by nematodes, the species being Ascaris transfuga and Spiroptera ( Gongylonema ) contorta of Molin. The latter is found in the œsophagus. Immature round worms have also been found in cysts. These were erroneously described as cestodes by Zeder and Gmel
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PART V (Pinnipedia).
PART V (Pinnipedia).
Following the order of classification adopted in my description of the Mammalia in the ‘Museum of Natural History,’ I proceed to speak of the internal parasites of the seals ( Phocidæ ) and walruses ( Trichecidæ ). From their piscivorous habits one would naturally expect the seals to be largely infested with entozoa, and yet, though sufficiently victimised, they are not liable to entertain so great a variety of helminths as the fishes themselves on which they feed. The flukes observed in Phoca v
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PART VI (Rodentia).
PART VI (Rodentia).
Though very numerous, the parasites of this order are chiefly interesting as embracing those of the hares and rabbits, moles, mice, rats, squirrels, and beavers. Some slight notice, however, will be given of the entozoa of each of the eleven families into which the order may be divided. The squirrels ( Sciuridæ ) are liable to be infested by the common liver fluke ( F. hepatica ), and also, it is said, by a cysticercus ( C. tenuicollis ). I have never encountered this bladder worm, but in 1864 I
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Part VII (Edentata).
Part VII (Edentata).
The entozoa of the edentulate mammals are not very numerous. So far as I am aware only one species has been described from the scaly ant-eaters ( Manidæ ). This is the small and probably immature ascaris noticed by Whitefield in the walls of the stomach of the badgareit or short-tailed pangolin ( Manis pentadactyla ). Amongst the true ant-eaters ( Myrmecophagidæ ) a single round worm has also been observed, but not adequately described. I allude to Marcgrav’s “find” in the little ant-eater ( Myr
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Part VIII (Ruminantia).
Part VIII (Ruminantia).
In the matter of parasites this order of mammalian animals stands second in importance. An entire volume of the dimensions of the present would barely do justice to the subject. Although in the article “Ruminantia” in ‘Todd’s Cyclopædia,’ and in my popular treatise on the mammalia, I have described the oxen ( Bovidæ ) and sheep ( Ægosceridæ ) as separate families, I shall here speak of their entozoa together; and, at the same time, I shall introduce occasional reference to the helminths of the a
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Part IX (Solidungula).
Part IX (Solidungula).
It will naturally be expected that I should give a full account of the parasites of the solipedal, solidungulate, or equine mammals. As regards the horse I regret that I cannot meet this expectation in so complete a manner as the subject deserves; nevertheless, with the aid of an extended bibliography the summary here offered will be found to be tolerably exhaustive. At all events I think I may say that no similar record has hitherto been attempted. The liver fluke ( Fasciola hepatica ), though
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Part X (Pachydermata)
Part X (Pachydermata)
Concerning the parasites and parasitic diseases of this miscellaneous assemblage of large mammals, I shall first speak of those of the proboscideans (Elephantidæ). Except by myself, they have been but little studied, and I am yet waiting for an opportunity to give further time to their consideration. When Diesing published his ‘Systema’ only two helminths were referred to the Indian elephant, namely, Ascaris lonchoptera and an undescribed fluke supposed to be a distome. The whole subject require
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Part XI (Cetacea).
Part XI (Cetacea).
The parasites of whales are excessively numerous. Unfortunately only a few of the species have been carefully studied, and much confusion necessarily exists as to the number of distinct forms. This statement is especially applicable to the entozoal group, which comprises upwards of a score of species. Probably Van Beneden has examined more of these parasites than any one else, and what little is known respecting them is for the most part due to his investigations. I have myself encountered and d
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Part XII (Marsupialia).
Part XII (Marsupialia).
The well-known fact that, in respect of their habits, the pouched mammals epitomise, as it were, the non-marsupial quadrupeds, would naturally lead us to look for a repetition of corresponding type-forms of entozoa as guests within their bodies. Speaking generally, the inference is correct; but very few of the entozoa hitherto found in marsupials correspond, as species, with those infesting man and non-pouched mammalia. A noteworthy exception occurs in the case of the common liver-fluke, which i
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SECTION II.
SECTION II.
To give an air of completeness to this treatise, I shall devote the few pages remaining at my disposal to a brief summary of the general facts of parasitism as witnessed in birds, reptiles, fishes, and evertebrated animals. For details I must refer to the separate original works and memoirs quoted in the appended bibliographies....
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Part I (Aves).
Part I (Aves).
A prodigious number of entozoa are known to infest birds. So far from birds being less victimised than mammals, the contrary is the case. Every now and then avian epizoötics, due to parasites, sweep off hundreds of these attractive hosts, and in some cases even nestlings are not secure from entozoal invasion. It might be supposed that predacious birds would be more liable to invasion than the graminivorous species. Such is not the case. The eagles, hawks, vultures, and owls certainly harbor a gr
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Part II (Reptilia).
Part II (Reptilia).
Much that I have advanced in respect of the parasitism of birds holds good in the case of reptiles. I cannot recapitulate. The saurians, ophidians, and chelonians are extensively infested, but in this respect the amphibian frogs, toads, and salamanders are probably the most victimised. If, on the one hand, comparatively few tapeworms have been found in reptiles, it may, on the other hand, be said that the Echinorhynchi come into prominence, causing serious injury to reptilian hosts. Serpents and
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Part III (Pisces).
Part III (Pisces).
Swarms of entozoa infest fishes, and it is hard to say whether they are less numerous in the inhabitants of fresh water than in those of salt water. More attention has been paid to the helminths of the fishes than to the internal parasites of birds and reptiles, consequently, the number of known species must be estimated by many hundreds. In like manner a great deal has been written respecting the ectozoa of fishes. These parasites, often called fish-lice, belong chiefly to the haustellated crus
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Part IV (Evertebrata).
Part IV (Evertebrata).
Since a large proportion of all those helminths that require a change of hosts must needs pass into the bodies of insects, crustaceans, mollusks, or other evertebrated animals, it is evident that these lower creatures are almost as liable to be infested by parasites as the vertebrates themselves. As a rule, no doubt, the parasitic forms infesting individual evertebrated hosts are not numerous; nevertheless the water-snails form a noteworthy exception. Thus, some ten different species of parasite
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