Entozoa

“ Possibly it is only by accepting the hypothesis of “Natural Selection” that we can escape the somewhat undignified conclusion that the entozoa were expressly created to dwell in us, and also that we were in part designed and destined to entertain them. View the matter as we may, the internal parasites of man and animals strictly conform to a few well-known types of structure, but these types branch out into infinitely varied specific forms. ”

“ Let it be freely granted that to the practising physician, as such, it matters little how many beasts, birds, reptiles, or fishes perish annually from parasitic affections; yet, when it is demonstrable that a large proportion of the strictly human entozoa require a change of hosts—or, in other words, need to pass through the bodies of the lower animals—then it is evident that some acquaintance on his part with the entozoa infesting animals becomes a practical necessity. ”

“ 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 crustaceans, and are better known by the title of Epizoa. ”

“ None of the internal parasites “continue in one stay;” all have a tendency to roam; migration is the soul of their prosperity; change of residence the essential of their existence; whilst a blockade in the interior soon terminates in degeneration and death. I repeat it. The entozoa constitute a specialised fauna. What our native country is to ourselves, the bodies of animals are to them. To attack, to invade, to infest, is their legitimate prerogative. ”

“ Although some attain their full development in the body of a single host—in this respect differing from all other Entozoa—the majority do not become sexually mature until after their transference from an “intermediate” to a “definitive” host. This migration is usually accompanied by a more or less complete metamorphosis, which is, however, not so conspicuous as in most other parasites, e.g. ”

“ I removed thirty-six worms from the œsophagus, proventriculus, and stomach, besides 166 others from the intestinal canal, thus obtaining a total of no less than 202 nematodes from this small host. Considering the large size of these entozoa, the extent of infection must be pronounced remarkable. The largest females measured 21/2′′ in length. One of the most interesting facts—serving to exemplify a well-known habit of lumbricoid worms generally—consisted in the circumstance that two of the parasites had succeeded in perforating the horny lining membrane of the gizzard. ”

“ The explanation is this:—Half of those 85,000 parasites, at the very least, will, in forty-eight hours after ingestion, have become fully-developed females; and from each of these 42,000 there will proceed at least 1000 as a brood, so that the entire progeny (and it is they that do the mischief by their independent migrations through our tissues) will eventually yield about 42,000,000 entozoa. If we should be so voracious as to eat a pound of such trichinised flesh, then there would be 400,000,000 as the result of a single meal. ”

“ Remembering that the Tape-worm, retaining its hold, continues to bud out such segments as fast as the fully-developed ones are cast off, and goes on doing this as long as the infested individual lives; we see that here, where there is no expenditure, where the cost of individuation is reduced to the greatest extent while the nutrition is the highest possible, the degree of fertility reaches its extreme. These Entozoa yield us further interesting evidence. Of their various species, most if not all undergo passive migration from animal to animal before they become mature. ”

“ In opposition to Leuckart, R. Moniez, however, is convinced that the migrations of the helminthes, as well as the system of intermediate hosts, represent the original order of things. Moniez traces all Entozoa from saprophytes, but only a few of these were able to settle directly in the intestine and there continue their development. These are forms that at the present day still lack an intermediate host, such as Trichocephalus, Ascaris, and Oxyuris. ”

“ I have received evidence of fatal epizoöty amongst chameleons from this source; and I have been requested to suggest a remedy. To prevent outbreaks of entozoal disease is one thing; to offer a radical cure when the parasites are firmly anchored within the pulmonary organs is quite another matter.
As remarked in my ‘Entozoa,’ the trematodes display a great partiality for batrachians, more than half a dozen different species of fluke being known to infest the common frog. Flukes are likewise tolerably abundant in the saurian and chelonian reptiles. ”

“ 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 ”

“ If, for example, we take the case of Trichina we find that several millions of entozoa may exist in the human, or, at all events, in the animal bearer, without producing any symptom of discomfort. In such cases it is not possible to determine the strict limits of health and disease; nevertheless, were we to double the amount of infection, the imaginary line of demarcation is at once bridged over and the parasites become acknowledged as directly responsible for grave symptoms which may even prove fatal to the bearer. ”

“ In the article above quoted the following passage occurs:—“Of all animals, feral or domestic, the common pig is beyond all doubt the most fertile source of human entozoa; at least, of important parasites, Trichina spiralis and the tapeworm would, there is good reason to believe, cease to infest us, did not this favorite quadruped act the part of a communicating medium.” ”

“ Where the entozoa are of minute size, and where their injurious action is primarily due to the mechanical obstructions they set up, it is clear that the virulence of the helminthiases, or resulting diseased conditions, will mainly depend upon the number of intruders. ”

“ Most people, not excluding even the votaries of the healing art, following tradition, regard the internal parasites or entozoa as creatures either directly resulting from certain diseased conditions of their hosts or as organisms which would not have existed if their bearers had been perfectly healthy. Nothing can be more absurd. ”

“ We have again the commoner parasitism of the Epizoa—animals which attach themselves to the surfaces of other animals, and feed on their juices or on their secretions. And once more, we have the equally common parasitism of the Entozoa—creatures which live within other creatures. ”

“ Expressly to meet the requirements of the Sanitarian I have dwelt upon the developmental phenomena exhibited by those parasites that occasion fatal helminthiases; and, in this relation, I have not confined my remarks to the parasites that are injurious to man in a direct manner, but have extended my observations to the genesis of those entozoa that prove destructive to horses, to beasts of burden generally, and to other creatures which, like cats and dogs, are in various ways subservient to man’s wants. ”

“ Press and Circular,’ Jan. 16th, 1867; again in the ‘Lancet,’ for March 13th, 1867; and in ‘Dublin Quart. Journ. of Medical Science’ for 1867, 3rd edit.; in the ‘Field,’ Sept. 25th, 1875; and in ‘Popular Science Review’ for Jan., 1876.—Idem, ‘Catalogue of the Specimens of Entozoa in the Museum of the Royal College of Surgeons of England,’ London, 1866; noticed in the ‘Lancet’ for March 24th, 1866, p. 321.—Idem, “On the best Methods of displaying Entozoa in Museums,” ‘Journ. Linn. Soc.,’ vol. viii, p. 170.—Idem, ‘New Entozootic Malady,’ &c., 1864; popular brochure, reviewed in the ‘Lancet,’ Feb. ”

“ Nevertheless, permanent parasites are also found in separate organs and systems, such as the muscular and vascular systems, hollow bones and brain, while some live on the outer skin. Here again, the terms Entozoa and Endoparasites do not include all stationary parasites; to the latter, for instance, the lice belong, which pass all their life on the surface of the body of their host, where they find shelter and food and go through their entire development. The ectoparasitic trematodes, numerous insects, crustacea, and other animals live in the same manner. ”

“ The White-blooded Worms or Entozoa are very imperfect animals, a fact which proves that this circle recommences quite inferiorly or from below. They live for the most part in the interior of other animals, being thus located in darkness and in places where they obtain but little oxygen. Their blood therefore is not simply colourless, but even its vessels are only imperfectly developed. They respire without doubt through the tegument. In many, a distinct or separate intestine being wanting, it is the tegument also which digests; in others the intestine is simply a sac without an anus. ”

“ Some of the data thus supplied are quite remarkable. Let me also add that my studies of the entozoa of wild animals have put me in possession of particulars of high value in regard to the larger question of the origin of epidemics. Beasts, birds, reptiles and fishes, of every description, are liable to succumb to internal parasites, and there is practically no end to the variety of useful information to be obtained from this source. ”

“ All these worms have been described by Molin, and, with the exception of the two first named, were new to science when he wrote his well-known monograph on the genus. They were collected by Natterer. All the species infest either the stomach or intestines, with the exception of Sp. spiralis. This singular worm, like the closely allied Sp. helicina, infesting the feet of birds, has the habit of coiling itself amongst the tendons of the digits of the hind limbs more especially.
Bibliography (No. 48) .—Cobbold, “On some new Forms of Entozoa,” ‘Linn. Trans.,’ vol. ”

“ Although the common liver fluke is flat, many species of the order are round, biconvex, or even filiform organisms. I recognise six families:—Monostomidæ, Distomidæ, Amphistomidæ, Tristomidæ, Polystomidæ, and Gyrodactylidæ. Most of the species are entozoal; but many adhere to the surface of the body of piscine hosts. ”

“ As regards the injurious effects of this parasite upon man, it may be said to act prejudicially in three separate ways. I have remarked in my ‘Entozoa,’ that this parasite may cause disease and death both by its action in the larval and adult states. It may likewise injure us by rendering the flesh of swine unwholesome.
When one or more sexually-mature tapeworms have developed themselves within the human intestine, they are apt to give rise to a variety of unpleasant symptoms, more or less marked according to the habit or irritability of the patient. ”

“ The Australian indigenous mammals have their own entozoa as a matter of course, and, in addition, they have contracted a few species from the domestic animals introduced into the country. On the whole, however, it cannot be said that the parasites of marsupials are of much practical consequence to agriculturists, since, with the exception of flukes, and probably hydatids, the Australian marsupials do not appear to harbor any entozoa that are likely to prove injurious to man and his domestic companions. ”

“ When the insect is not examined till the third day, the contained parasites will probably manifest marked signs of disintegration—and possibly every indication of life will have disappeared from many of the specimens. After the third or fourth day I have not seen any active specimens of these entozoa in the stomach or in any part of the alimentary canal of the mosquito; those which remain have undergone more or less fatty degeneration, and are readily stained with eosin, which, as far as my experience goes, is not the case so long as they are alive and active. ”

“ Weekes, who claim to have produced animalcules in considerable numbers, of a species before unknown, by passing a voltaic current through silicate of potash, and through nitrate of copper. The existence of entozoa, or parasitic animals, found in the interior of the bodies of other animals, and found nowhere else, is thought to support the same doctrine. ”

“ 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. ”

“ The majority of germs calculated to engender parasites are to be found in abundance in the contents of the alimentary canal of human beings and domestic quadrupeds. If pigs are permitted to eat these, as in Ireland or in many British piggeries, we must expect hams, bacon, and pork sausages to be charged with the embryonic forms of human entozoa. ”