Fig. 59.—Ascaris osculata. a, Male; b, female. Natural size. Original.
The flukes observed in Phoca vitulina are Distoma acanthoides and Amphistoma truncatum, the latter occurring also in P. grœnlandica. In another seal (P. barbata) we have D. tenuicolle. The nematodes are more numerous. The best-known is the maw-worm (Ascaris osculata), which seems to be always present in full-grown seals of every kind. In the years 1862–64 I conducted a series of experiments with the eggs of this worm. I reared embryos both in salt and fresh water, but the administration of the young worms to various animals led to no result. However, I succeeded in watching the growth of the embryos until they had acquired well-marked digestive organs and a length of 1/25″, their size when emerging from the egg-shell in the water having been about 1/150″ only. The large strongyle (Eustrongylus gigas) has been found in various organs of the common seal. Of more interest are the Filariæ found in the heart of seals, which in many respects resemble those obtained from the same situation in dogs. Professors Joly, Leidy, and myself, have each described a species, but apparently our descriptions all refer to one and the same parasite. It has also been seen by Camill Heller. The close correspondency in size and other characters of Leidy’s Filaria spirocauda and my Filaria hebetata leaves little doubt as to their identity. As the worms were both originally noticed by Leidy and Joly in 1858, I cannot pronounce upon the question of priority of discovery. By Joly the worm was called F. cordis phocæ. In Leidy’s and in my own specimens the males were four inches long, and the females six inches; they extended up to 8″ in some of the American examples. The worms found by Prof. Joly were all females. Professor Millen Coughtrey, who furnished me with the seal’s heart, stated that it was obtained from a male hoodcap (Stemmatopus cristatus), a rare visitant of our British coasts. This seal was captured on the Cheshire side of the Mersey river. Leidy and Joly obtained their specimens from Phoca vitulina. In the common seal have also been found Ligula crispa, Schistocephalus dimorphus, and Echinorhynchus strumosus. In other seals a not uncommon tapeworm of the Bothriocephalous type is that called Dibothrium hians by Diesing. To Prof. Krabbe I am indebted for a specimen of Bothriocephalus fasciatus taken from Phoca hispida. There is a nematode of frequent occurrence in P. hispida and P. grœnlandica. This is the Ophiostoma dispar of Rudolphi. In addition to the above I can only add that P. barbata is infested by Liorhynchus gracilescens, occupying the stomach, and by a tapeworm, Tetrabothrium anthocephalum, which is found in the lower part of the large intestine.
Bibliography (No. 46).—Cobbold, “Description of F. hebetata,” in ‘Notes on Entozoa,’ part i, sp. 3, ‘Proc. Zool. Soc.,’ Nov. 18th, 1873, p. 741.—Idem, “On Ascaris osculata,” in ‘Report of Experiments respecting the development and migrations of the Entozoa;’ ‘Brit. Assoc. Trans.,’ 1864, p. 114.—Heller, C., in ‘Schrift der zool.-botan. Gesellsch.,’ Wien, 1858, s. 83.—Joly, “On a new Species of Hæmatozoon of the genus Filaria, observed in the heart of a seal;” from ‘Compt. Rend. Acad. Sci.,’ 1856, p. 403, in ‘Ann. Nat. Hist.,’ vol. i, 3rd ser., 1858; also abstr. in the ‘Year Book,’ 1859.—Leidy, J., (E. spirocauda) in ‘Proc. Philad. Acad.,’ 1858, p. 112.
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 described some polycephalous hydatids (Cœnuri) which I obtained from the viscera of an American squirrel. I think the host was of the same species (Sciurus vulpinus) as that from which Mr Chapman has since obtained an example of Echinorhynchus (E. moniliformis). This worm also infests the hamster. A very small female round worm, probably a strongyle, was described by Rudolphi as Ascaris acutissima. It infests the cæcum of the common squirrel, in which host a species of tapeworm is tolerably frequent (Tænia dendritica). The common European marmot is infested by T. pectinata, so abundant in hares and rabbits. I have also noticed it as occurring in the Canadian porcupine (Hystrix dorsata). The dormice (Myoxidæ) are not much troubled with parasites, at least I have not encountered any in our common Myoxus avellanarius. In M. glis, however, a tapeworm, and at least one species of strongyle (S. gracilis), have been observed. Dujardin described very fully another strongyle (S. lævis) from M. nitela, from the long-tailed field-mouse (Mus sylvatica), and from Arvicola subterraneus. The other species are Trichosoma myoxi nitelæ, and Ophiostoma cristatum from Myoxus dryas, and M. muscardinus. The jerboas (Dipodidæ), in common with the hamster and several species of true mice, are apt to be infested by Ascaris tetraptera; and a small nematoid, apparently immature, was noticed by Otto in the intestines and in the abdominal walls and cavity of Dipus tetradactylus. Mice, properly so called, are largely infested, as is also the hamster (Cricetus vulgaris), which I include in the Muridæ. In addition to the parasites already mentioned, the hamster is infested by Tænia straminea. Along with examples of this tapeworm I have received from Dr Murie some acephalocysts found in a hamster which died at the Zoological Gardens.
Flukes exist in the long-tailed field-mouse (Distoma vitta and D. recurvum), but I have not seen any in our common mice and rats. However, Dujardin describes a distome (D. spiculator) in the brown rat (Mus decumanus). One of the tapeworms observed in the mouse (M. musculus) is Tænia pusilla, also found in the rat (M. rattus) and long-tailed field-mouse. The house-mouse likewise harbors T. microstoma and T. leptocephala; and an immature cestode has also been seen in the abdomen, probably a species of Ligula. Various species of rat also harbor T. diminuta. In regard to the round worms one of the most common species is Ascaris oxyura. This not only occurs in rats and mice, but also in voles, water-rats, and many other rodents. The rodents’ whipworm (Trichocephalus nodosus) is yet more common in the lemmings, rats, voles, and mice; another species (T. unguiculatus), taking its place in hares and rabbits, and yet another (T. affinis) in the porcupine. Another nematoid, very common in mice, is Spiroptera obtusa, occupying the stomach. I have seen a mouse with its abdomen so distended by their presence that the animal could scarcely run along the pathway where it was killed by being trod upon. According to Marchi, the young of this entozoon dwell in the fat surrounding the alimentary canal of the larva of an insect (Tenebrio molitor). When noticing the parasites of the cat I referred to Leuckart’s interesting discovery of the relations subsisting between the adult Olulanus tricuspis, found in the stomach walls of that feline, and the immature encysted worms, found not only as wanderers in the cat itself but also in the muscles of mice. The olulanised mouse is thus an intermediate host. Rats and mice also play the part of intermediary bearers in the case of two other species of entozoa, namely, Trichina spiralis and Tænia crassicollis, the tænioid scolex or larval condition of the cat’s tapeworm being familiarly known as Cysticercus fasciolaris. This sexually-immature tapeworm infests many other rodents, especially the voles (Arvicolidæ). In regard to Trichinæ it must not be forgotten that their presence in rats is not uncommon in some parts of Europe; and this circumstance may explain the recurrence of trichinosis (first in hogs and then in man) in certain outlying districts. Only in this way can the Cumberland outbreak in this country be accounted for. Here I cannot dwell upon the subject, but in this connection I may observe that Bakody has in a very convincing manner described a new variety or species of Trichina, found by him infesting the walls of the stomach and intestine of rats. In the first instance he detected the worm in association with the ordinary T. spiralis, but afterwards separately. He also obtained it in fowls. The species should be called Trichina Bakodyii. Possibly the nematodes observed by Colin in 1863 also refer to this worm. They occupied tubercles in the liver of a rat. In regard to the beavers (Castoridæ) it appears that they harbor many species of round worms, and also several flukes, but they do not appear to have been very much studied. In Morgan’s work on the American beaver there is a notice in which it is stated that Dr Ely found a very fine filamentous worm [40‴] in length. This does not seem to correspond with Ascaris castoris (Rud.). He also speaks of large numbers of a slender white worm, 3″ to 5″ in length, found in the peritoneal cavity, and referable to the genus Filaria. This cannot be confounded with Trichocephalus castori (Rud.). Moreover, he describes a strongyle (Sclerostoma) as infesting the colon, and especially the cæcum. These all appear to be new to science. The Fasciola hepatica is occasionally found in the liver, but the most common helminth of beavers is Amphistoma subtriquetrum. Specimens of this worm may be seen in the British and Hunterian Museums. As regards the porcupines (Hystricidæ) I have already mentioned the occurrence of a tapeworm in the common species. The larval Pentastoma denticulatum has been found by Otto attached to the surface of the lungs, and Redi, about two centuries back, noticed small nematodes lodged in tubercles of the œsophagus. The late C. M. Diesing obtained Trichocephalus affinis from the intestines. So far as I am aware, little or nothing has been said respecting the helminths of the Octodontidæ, Chinchillidæ, and Cavidæ. Like other European investigators I have dissected guinea pigs (Cavia aperœa) without finding any parasites; but in Brazil a small species of ascaris (A. uncinata) was found by Natterer in this animal and also in the paca (Cœlogenys paca). The agoutis (Dasyprocta) harbor Trichocephalus gracilis.
The entozoa of the duplicidentate rodents (Leporidæ) acquire importance from the fact of their abundance and from the intimate relation which some of them bear to parasites infesting the dog and other animals. Thus, the two commonest kinds of fluke infesting cattle (Fasc. hepatica and Dist. lanceolatum) also attack hares and rabbits; the former parasite often producing the rot disease, which is almost as fatal to the rodents as it is to the ruminants. Mutual infection occasionally results from this circumstance by the distribution of germs. All experiment-conducting helminthologists have reared Tænia serrata from the Cysticercus pisiformis; nevertheless, several English Manuals of Zoology persist in propagating the old error of Von Siebold, who supposed he had reared this tapeworm by the administration of Cœnuri. So far as I am aware, no feeding experiments have been conducted with the Cœnuri of rabbits (C. cuniculi). These bladderworms infest the soft parts of the body, often producing tumours having a very unsightly appearance. For details I must refer to the papers quoted below. The Norfolk warreners call the infested hosts “bladdery rabbits.” Though apparently most abundant in the eastern counties of England, these diseased rabbits are by no means confined to that quarter. Through Mr Alston’s help I have received specimens of Cœnurus cuniculi from Ayrshire, Scotland. Probably this form of Cœnurus occurs wherever rabbits live. In Italy a case is recorded by Perroncito from the abdominal cavity of a rabbit (coniglio). Every experimenter is more or less familiar with the cestode larvæ (C. pisiformis) found wandering in the abdominal cavity. These were regarded as flukes by Kuhn (Monostoma leporis). I need hardly remark that the developmental and structural changes undergone by these Cysticerci during their residence within the rabbit have been exhaustively followed out and treated of by Leuckart. Without dwelling on this subject, I must in justice add that in this relation the special labors of Küchenmeister, Van Beneden, Haubner, Wagener, Röll, Eschricht, and Möller played no inconspicuous part. My own efforts in 1857, and subsequently, were not unattended with success. It therefore seems to me, without prejudice to the recent experiences of De Sylvestre and others, that further experiments in this immediate connection are unnecessary. As regards the nematodes of leporine rodents, probably the most important is Strongylus commutatus. This parasite, like its husk-producing congeners, infesting calves and lambs, occasionally sweeps off great numbers of hares. Such an epizoöty occurred in Thuringia in 1864. The most frequent intestinal parasite of rodents is probably Oxyuris ambigua, but Strong. retortæformis is tolerably abundant in the hare, and Trichocephalus unguiculatus is liable to occur in all leporines. I know nothing of the so-called Strong. strigosus of rabbits, but Bellingham found it in Ireland. Olfers and Natterer obtained a small ascaris (A. veligera) from Lepus braziliensis; but I cannot help thinking that the large measle (Cysticercus macrocystis) described by Diesing as three inches in length, and obtained from the same rodent, must either have been Cœnurus cuniculi or else another form of polycephalous hydatid.
In reference to the ectozoa of rodents it may be said that they are very numerous. Acari infest rats and mice, and especially leporines. Thus, in the mouse are found Sarcoptes notoedre, Bourguignon, var. muris, Mégnin, Sarc. musculinus, Koch, and Myobia musculi, Claparède. It is not very generally known that wild rabbits are apt to be attacked by the common autumnal spider (Leptus autumnalis), whence, as once happened with myself, they may be transferred to the human body. The ears of tame rabbits are sometimes covered with acari, which are easily destroyed by the cautious application of a mixture of carbolic acid and olive oil (one of acid to six of the oil). Rodents also harbor fleas. At a meeting of the Entomological Society in 1875 Mr Vernall showed living specimens from the ears of a rabbit, and Messrs Cole and W. A. Lewis stated that they had obtained fleas from the hedgehog and European marmot respectively.
Bibliography (No. 47).—Beneden (see Van Beneden below).—Capelle, J., Extr. from a letter, in which the author states that he had “found worms of the tænia kind in the liver of sixteen out of eighteen rats,” ‘Med. Commentaries,’ vol. xix, p. 139, 1794; see also ‘Trans. Coll. Phys. of Philad.,’ vol. i, part ii, p. 60, 1793.—Chapman, H. C., “Echinorhynchus in Squirrel,” ‘Proc. Acad. Philad.,’ 1874, p. 76.—Cobbold, “Note on Cœnurus (from a squirrel),” ‘Proc. Linn. Soc.,’ May 5, 1864.—Idem, “On the occurrence of Tænia pectinata in the Porcupine (Hystrix dorsata),” in a letter to Dr Lawson in the ‘Canadian Naturalist and Geologist,’ 1862.—Idem, ‘On T. serrata,’ &c. (see Bibl. No. [45]).—Colin, “On the presence of a Nematode Worm in certain Tubercles of the Liver of a Rat,” from ‘Rec. de Méd. Vét.,’ in ‘Edin. Vet. Rev.,’ Oct., 1863.—Leuckart, ‘Die Blasenbandwürmer (u. s. w.),’ 1858 (contains numerous details and figs. in ref. to Cysticercus pisiformis and T. serrata, &c.).—Marchi, P., ‘Mem. della R. Accad. d. Sci. di Torino,’ xxv.—Peacock, “Remarks on the Liver of a Mouse with Cysts containing Cysticerci,” ‘Lancet’ and ‘Trans. Path. Soc.,’ 1855.—Perroncito, E., “Sopra un caso di Cœnurus (in the abdominal cavity of a rabbit),” ‘Giornale Med. Veter.,’ 1876.—Siebold (see Von Siebold, below).—Sylvestri, De, “Experiments with C. pisiformis,” ‘Il. Med. Veterinario,’ 1871.—Van Beneden (see Bibl. No. [45]).—Idem, “On Sciurus glacialis and its Parasites,” from ‘Bull. de l’Acad. de Belgique,’ in ‘Ann. Nat. Hist.,’ vol. xiii, 1854.—Verrall, in ‘Proc. Ent. Soc. Lond.,’ Feb. 15, 1875, p. 3.—Von Siebold, ‘Ueber die Band-und Blasenwürmer,’ Leipsig, 1854, and Huxley’s edit. for Syd. Soc., 1857.—Idem, “Experiments on the Transformation of the Cystoid Worms into Tænias,” from ‘Ann. des Sci. Nat.,’ in ‘Ann. Nat. Hist.,’ vol. x, 1852.—Idem, “Helminthology,” trans. by Busk and pub. in ‘Ray Soc. Rep. on Zool.,’ 1843–44, p. 446, London, 1847.—Idem, “On the Transformation of Cysticercus pisiformis into Tænia serrata,” from ‘Zeitsch. f. w. Zool.,’ in ‘Quart. Journ. Micr. Sci.,’ 1854.