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 (Pallas, Brera, Bidloo, Malpighi) and gall-bladder (Partridge). The alleged cases by Bauhin, Wepfer, and Chabert are spurious, as is probably also that given by Mehlis. Duval’s case appears to be genuine, but the occurrence of the worm in the portal vein was accidental. Dr Murchison has recorded a case, occurring at St Thomas’s Hospital, where a solitary specimen was found in the liver. Dr H. V. Carter also met with the worm in a young Hindoo.
In the second half of the present work I shall reproduce Blanchard’s admirable figure of the sexually mature worm (Fig. [61]), accompanied by a categorical statement respecting the known facts of development. In this place, however, I may observe that the cases recorded by Giesker, Harris, and Fox had clearly pointed to the circumstance that the higher larvæ of this fluke must be armed cercariæ, otherwise they could not have bored their way through the human skin. As we shall see, Dr Willemoes-Suhm’s investigations have furnished evidence as to the truth of this supposition. For anatomical details I refer to my introductory treatise. In the adult state the liver fluke has been known from the earliest times. We have clear evidences that it was described by Gabucinus in the year 1547, and also subsequently by Cornelius Gemma, who, in a work published some thirty years later, refers to an epizootic disease prevalent in Holland during the year 1552, and which was very justly attributed to the parasite in question. After this date many writers described the liver fluke more or less accurately, and entire volumes were devoted to the consideration of the formidable disease which it occasions. The nomenclature of the parasite has been a subject of controversy. Amongst naturalists in general the common liver fluke is often described under the combined generic and specific name of Distoma hepaticum; but the title is both incorrect and inappropriate. The proper generic appellation of this parasite is Fasciola, as first proposed by the illustrious Linneus (1767) and subsequently adopted by F. Müller (1787), Brera (1811), Ramdohr (1814), and others. Unfortunately Retzius (1786) and Zeder (1800) changed the generic title without good cause, and the majority of writers, following their authority, refused to employ the original name, although a consideration of the distinctive types of structure severally displayed by the genera Distoma and Fasciola fairly demanded the retention of the Linnean title. In later times M. Blanchard (1847) strongly advocated the original nomenclature, and I have myself continually urged its adoption. On somewhat different grounds Professor Moquin-Tandon followed the same course.
In the sexually mature state the liver fluke commonly measures three fourths of an inch in length, occasionally reaching an entire inch or even sixteen [lines]; its greatest breadth also varying from half an inch to seven or eight lines transversely; body very flat, presenting distinct dorsal and ventral surfaces, frequently curled toward the latter during life; upper or anterior end suddenly constricted, produced and pointed in the centre, forming the so-called head and neck; posterior extremity less acuminated, sometimes rounded, or even slightly truncated; margins smooth, occasionally a little undulated, especially towards the upper part; oral sucker terminal, oval, rather smaller than the ventral acetabulum, which is placed immediately below the root of the neck; reproductive orifices in the middle line, a little below the oral sucker; intromittent organ usually protruded and spirally curved; a central, light-coloured space, covering two thirds of the body from above downwards, marks the region of the internal male reproductive organs, being bordered on either side and below by a continuous dark band, indicating the position of the so-called yolk-forming organs; a small, brown-coloured, rosette-like body situated directly below the ventral acetabulum, marks the limits of the uterine duct; a series of dark lines, branching downwards and outwards on either side, indicate the position of the digestive organs; general color of the body pale brownish yellow, with a slight rose tint. The surface of the body, though smooth to the naked eye, is clothed throughout with small epidermal spines which diminish in size towards the tail.
If any argument were necessary to show how desirable it is to furnish full descriptions of the commoner kinds of parasite, I could adduce numerous instances that have been brought under my notice where professional men and others have been entirely mistaken as to the essential nature of their parasitic finds. Thus, I have known an instance where a great authority on the diseases of dogs has persisted in asserting for the free proglottides of a tapeworm a nematode origin; and, in like manner, human tapeworm-segments have frequently been mistaken for independent fluke parasites. One of the most remarkable instances of this kind is that which I have elsewhere described as an error on the part of Dr Chabert. My reasons for so regarding his interpretation of the facts observed by him stand as follows:
In the ‘Boston Medical and Surgical Journal’ for the years 1852–53–54, Dr J. X. Chabert described several cases of Tænia, and he averred that the tapeworms were associated with numerous specimens of Distoma hepaticum. The passage of distomes by patients during life was even regarded by Dr Chabert as indicative of the presence of Tænia within the intestines. Surely, I remarked, Dr Chabert was mistaken. Are not these so-called distomes the well-known proglottides? Not willingly doubting Dr Chabert’s statements, but desirous, if possible, of verifying the accuracy of his conclusions, I wrote to him (March 22nd, 1864) requesting the loan of a specimen, but I was not fortunate enough to receive a reply. In the “Case of Tænia” in a boy four and a half years old, given in the 49th vol. of the journal, Dr Chabert writes as follows:—“In consequence of his passing the Distoma hepaticum, I concluded he must be afflicted with Tænia.” Further on it is added, that the administration of an astringent injection “caused the discharge of innumerable small worms (Distoma hepaticum).” I think this is quite decisive. The idea of “innumerable” flukes being expelled in this way is altogether out of the question.
The only genuine case in which any considerable number of Distomata, of this species, have been observed in the human subject is the one recently recorded by Dr Prunac. In this instance two flukes were vomited along with blood immediately after the administration of salines (sel de Seignette), and about thirty were passed per anum. On the following day, some tapeworm proglottides having been evacuated, both salts and male-fern extract were administered. This caused the expulsion of an entire tapeworm, and also about twenty more flukes. Notwithstanding this successful treatment the hæmatemesis returned in about a month, when, finally, three more flukes were vomited and the bleeding ceased. Had not the parasites been submitted for identification to a competent observer (Prof. Martins, of Montpellier), some doubt might have been entertained as to the genuineness of this remarkable case. In reference to Dr Prunac’s comments on the facts of fluke-parasitism in man, I will only remark that Dr Kerr’s Chinese cases, to which he refers, were probably due to Distoma crassum and not to D. hepaticum. The Chinese flukes will be noticed below.
Bibliography (No. 3).—Full references to details of the cases by Partridge, Fox, and Harris are given in Appendix B. to Lankester’s Edit. of Küchenmeister’s Manual. See also the works of Davaine and Leuckart (l. c. Bibl. No. 1).—Carter, H. V., “Note on Distoma hepaticum” (from a patient under the care of Mr Pandoorung), ‘Bombay Med. and Physical Soc. Trans.’ (Appendix), 1862.—Chabert, J. X. (quoted above). Murchison, C., ‘Clinical Lectures on Diseases of the Liver,’ (2nd Edit., Appendix), London, 1877.—Prunac, De la Douve ou Distome hépatique chez l’homme; in ‘Gazette des Hôpitaux’ for December, 1878 (p. 1147). For further references in this work, see Bibliog. No. [49].
Fig. 1.—The lancet-shaped fluke (Distoma lanceolatum), showing the disposition of the digestive and reproductive organs internally. Viewed from behind; mag. about 12 diameters. After Blanchard.