Cornell University Library The original of tiiis book is in tine Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. http://www.archive.org/details/cu31924024780607 Cornell University Library QL 392.C66 Entozoa: 3 1924 024 780 607 *.... ENTOZO A. lasciola gigantea, Cobbold. Magnified 2; diameters. T. S. a delt. EN T Z A : AN INTRODUCTION TO THE STUDY OF HELMINTHOLOGY. ■WITH KEFEHESCE, MORE PARTICULARLY, TO THE INTERNAL PARASITES OF MAN J" BY T.^SPENCEE COBBOLD, M.D., E.E.S., LECTUREE ON COMPABATIVE ANATOMY AT THE MIDDLESEX HOSPITAL. LONDON: GROOMBRIDGE AND SONS, 5, PATERNOSTER ROW. MDOCCLXIV. CORNELL liNIVERSITYi LIBRARY ■>- -»^«, DEDICATION. TO GEORGE BUSK, Esq., P.R.S. Deak Mr. Busk, I request you to accept tlie dedication of this Elementary Treatise on a subject which so much engaged your attention during the earlier period of youi- scientific career. The advice and encouragement received at your hands during several years past have materially aided me in the prosecution of those entozoologioal investigations which form the basis of this volume ; and, but for the important series of drawings which your skilful pencil and disinterested kindness have supplied, the work, as it now stands, must have been deprived of one of its most attractive features. I am, dear Mr. Busk, Tours very truly, T. SPENCER COBBOLD. PREFACE. Without any customary apology, either to the general public or to the members of the medical profession, I introduce this elementary treatise. On all hands it is conceded that the subject of Entozoology has an important bearing on questions affecting the maintenance of public health ; and it is to be regarded as a matter of congratulation that the political economist of the present day not unfrequently avails himself of the labours of the scientific naturalist. Since the publication of Mr. Rhind's snaall volume on the internal parasites of the human body, so far back as the year 1829, I am not aware that any complete work of a similar kind has been written by any English author. It is true that we are in possession of several original and extremely valuable memoirs which will bear advantageous comparison with the more numerous hrochures Issued in foreign lands ; but, as regards works designed to embrace the study of Hel- minthology, in its entirety, no such project has hitherto been attempted. The void, however, has been more or less completely occupied by several able transla- tions. First and foremost among these is the Sydenham Society's edition of Kiichenmeister's standard work on the "Animal and Vegetable Parasites of the Human Body," by Dr. Lankester, F.R.S. Secondly, we are presented with a tolerably comprehensive outline both of the external and internal parasites of man, in Mr. Huhne's edition of Moquin-Tandon's useful little book, entitled Elements de Zoologie Mtdicale. Thirdly, we are furnished with an excellent account of the general organization of the Helminths and Turbellarians in the fifth and sixth sections of Dr. Burnett's American edition of Von Siebold and Stannins' Lehrhucli der verf/leichenden Anatomie ; and, fourthly, there is Dr. W. A. Smith's recently issued volume "On Human Entozoa," which is, for the most part, an agreeable and practical excerpt from Davaine's remarkable Traite des vm PREFACE. JEntozoaires et des Maladies Vermmeuses de V Homme et des Animaux Domestigues. Besides these, it may not be out of place to particularize Prof. Huxley's transla- tion of Von Siebold's memoir on Tape and Cystic "Worms {Band und JBlasm- wurmer), and especially, also, Weinland's " Essay on the Tapeworms of Man," ■written in the English language by its accomplished author. In respect of original contributions on Entozoa, it were almost invidious to refer to particular articles and papers ; yet I may, perhaps, be permitted to acknowledge the pleasure and profit I have derived from a perusal of the writings of Owen, Busk, Huxley, Thomson, Nelson, Carter, and Bastian. The engravings of this work have been executed with great care. The twenty- one Plates comprise one hundred and fifty-six separate figures, which, with eighty- two Woodcuts, make a total of two hundred and thirty-eight Illustrations. Of these, one hundred and five are derived from original sources ; forty-three are taken from drawings executed by Mr. Busk ; twenty-four are small figures, in one Plate, from Nelson ; nineteen, mostly large Woodcuts, from Leuckart ; thirteen, more or less completely, from Blanchard ; six from figures by the late Professor W. Smith, of Cork ; six from Van Beneden ; four from Kiichenmeister ; three from Huxley ; two from Eberth ; and one each from Van Ammon, Wilson, Rokitansky, Bristowe and Rainey, Curling, Claperede, Hulke, Lubbock, Bastian, Knoch, J. Harley, and Mosler. To this list may be added also the illustration so ably executed by Mr. Jennens (at p. 124) from a photograph by Dr. Hallifax of Brighton. The extended Bibliography attached to this work is the result of a laborious search after entozoological facts, scattered through upwards of twelve hundred British and American volumes. No one, who has not gone over our home literature after this fashion, could have believed what a multitude of valuable and instructive data lie concealed within the shelves of our public libraries. To the council of the Royal College of Surgeons of England, and to Mr. Chatto, their obliging Librarian, I am greatly indebted for the liberal manner in which I have been permitted access to their library ; and only in a less degree are my obligations due to Professor James Beart Simonds, of the Royal Veterinary College, for the free use of his private and valuable collection of professional works. The libraries of the Linnean and Zoological Societies, as well as those of the Mid- dlesex Hospital Medical College and Royal Medico-Chirurgical Society, also supplied me with useful references. PREFACE. IX As regards foreign Kterature, I have scarcely had occasion to go beyond the tolerably complete collection of works which (thanks to the vigUance of Messrs. Wi lliam s and Norgate) my private shelves contain ; but, in this connection, I beg to offer my acknowledgments to D. F. Weinland of Frankfort, C. M. Diesing of Vienna, E. Claparede formerly of Geneva, and R. Leuckart of Giessen, for their kindly gifts. T. S. 0. MroDMiSEX HospiTAii Medicaii Coiij;qe, London, September, 1864. CONTENTS. PART I. SYSTEMATIC HBLMINTHOLOGY. CHAPTER I.— TUEBELLAMA. Nature and extent of the subject— Leading terms employed— The Entozoa constitute a peculiar /aMwo — Their distribution throughout time and space — ^Not yet found in a fossil state — ClassiScation of the Helminths — A new sub-class proposed — The Tur- beUarians — Characters of the Planaridse — Grenera — The Nemertidse, or ribbon worms — Their structure and habits — Grenera — Concluding argument in favour of associating the TiirbeUarians with the Helminths in the manner here proposed. P. 2—13 CHAPTER II.— Tbematoda. The Trematoda, or flukes — Aspect and habits— Distribution in mammals, birds, reptiles, and fishes— Estimated number of species — Classification of the order — The family of Monostomes — Their development and genera — The Distomes — Their anatomical structure and development — ^Van Beneden's investigations respecting Distoma mili- tare — Pagenstecher's researches — Genera 14 — 32 CHAPTER III.— Teematoda. Structure of particular Trematode types — Fasciola — Grasterostoma — Campula — BUharzia — ^Echinostoma — Family of the Tristomes — Their development and Genera — The Polystomes — Genera — The Gjrodactyles — Wedl's researches I'especting their orga- nization — Development — Von Siebold's ,and Van Beneden's opinions contrasted. 33-51 XU CONTENTS. OHAPTBE IV.— Nematoda. The order of round worms, or Nematoda— Aspect, habits, and distribution— Probable number of known species— Classification— AnguillulidEe— The common viaegar eel as a type— Genera— Gordiidee, or family of hair-worms— Dujardin's account of the structure of Mermis nigrescens— The views of Meissner, Von Siebold, and Van Be- neden respecting the development of Mermis— Genera— Structure of Sphaerularia — Oxyuridse, or thread-worms — Organization of Oxyuris eurvula—Orenera. . P. 52 — 67 OHAPTBE v.— Nematoda. The Filaxidse — Triohoeephalus affinis considered as a type — "Wilson's investigations respecting its anatomical structure — The views of Kuchenmeister and of Eberth regarding the characters presented by the reproductive organs, compared with those severally entertained by Mayer, Eberth, and the Author— Embryonic develop- ment — Genera — Simondsia paradoxa — Oheiraoanthidse — Genera — ^AscaxidEe — Genera. 68—82 OHAPTBE VI.— K"bmatoda. StrongylidsB — Genera — The Sderostoma syngamus as a type, with a particular account of the gape disease which it occasions— Structure and development — Remedial methods — The genus Prosfhecosacter—Ovgasnz&iiioTL of Prosthecosacter convolutus — Mode of reproduction — Oucullanidse — Genera 83 — 96 OHAPTBE VII.— Acahthocephala. Acanthocephala or Thorn-headed worms — General characters and distribution — Olassi- fioation — Organization of Echinorhynchus anihwis. Singular mode of egg-forma- tion— Leuckart's researches respecting the development oi Echinorhynchus proteus — His discovery of the so-called phenomenon of " alternate generation" in this class of parasites 97 — 103 OHAPTBE VIII.— Oestoda. Oestoda or Tapeworms — General characters and habits — Distribution in mammals, birds, reptiles, and fishes — Estimated number of species — Tffiniadse — Particular account of the development of Cysticercus pisiformis from the eggs of Tcenia serrata, and also of the adult tapeworm from the Oysticercus — Constitution of the " zoological indi- vidual" — Genera . . . . . . ... 104 — 115 CONTENTS. Xlll CHAPTBE IX.-CESTODA. Particular larvse — Ccenurus cerehralis of the sheep — Rose's discovery of a second kind of Coeniu'us — Several other forms now known — Numan's observations — The Cysti- cercus tenuicolUs and C fasciolaris — BothriocephalidEe — Structure and develop- ment — Genera — Diphyllohothrium and SWcttspiciarja— Tetrarhynchidee — Structure, habits, and development — Genera .P. 116—141 PART II. SPECIAL HBLMINTHOLOGY. OHAPTBB, I.— Tkematoda. Importance of experimental research in human hehniuthology — Species of entozoa infesting man— The common liver fluke, or Fasciola hepatica—GwLer&\ and specific characters— History and nomenclature— Distribution and descriptive anatomy- Comparison with Fasciola cfiffantea— Special structural pecuharities . 145 — 163 CHAPTER II.— Fasciola hepatica. Development oi Fasciola hepatica — Eggs and ciliated embryos — Injurious effects of the liver-fluke upon man and animals — Symptoms produced by the Rot — Pathological appearances — Treatment — Summary ... .... 164 — 183 CHAPTER III. — DisTOMA lanceolatum. Flukes with a simple unbranched intestine — Distoma lanceolatwm — General and specific characters— Its non-identity with Fasciola hepatica— Kichner's interesting case — Leuckart's account of the embryo — Distoma ophtAalmobium, — D. crassum and D. heterophyes — Bilharzia hoematohia — General and specific characters — Structure and development — Injurious efiects on man — Tetrastoma venale — Hexathyridium pinguicola and 3. venarum . . 184 — 207 XIV CONTENTS. CHAPTER IV.— Obsioba. General considerations respecting the origin of human tapeworms— Kuchenmeister's great merit in establishing the experimental method of research — The inferences of MM. Pouchet and Verrier successfliUy opposed by Van Beneden — Tarda solium — General and specific characters— Name and history — Anatomy of the strobile and proglottis — Egg and six-hooked embryo — Measle, or Cysticercus celluloses P. 208 — 219 CHAPTER v.— TiENiA solium. Development of the common tapeworm — The life-phases of Tania solium regarded as parts of the "zoological individual" — Injurious effects upon man — Particular instances — Frequency of Oysticerci in the human brain— Mr. Hulke's case — ^Pre- cautions suggested — Statistics — Treatment . . . 220 — 234 CHAPTER VI. — T^NiA. mediocaubllata. General and specific characters of Tama medioeanellata — Feeding experiments of Leuckart and Mosler — Acute cestode tuberculosis — Statistics — Kaschin's account of the prevalence of tapeworm amongst the Cossacks of the Baikal — Tcmia acantho- trias, T. flavopuncta, and T. nana — Probable identity of Tcenia elliptica with T. cucumerina — Structure of the so-called Oysticercus tenuicollis, or larva of Tmnia marginata 235 — 252 CHAPTER VII.— T^NiA echinoooccus. General and specific characters of the Tmnia echinococcus — Grounds for disputing Kiichenmeister's notion that there are two distinct forms of Eohinococcus — Struc- ture and development of the adult worm — -Hydatids — Exogenous, endogenous, and multUocular varieties — Growth and structure — Formation of the scolices within brood capsules — Opinions of Owen, Wilson, Busk, Huxley, Naumyn, and Leuckart, severally contrasted .... .... 253 — 272 CHAPTER VIII.— T^NiA ECHmoooccus. Hydatids considered from a professional point of view — Leuckart's condensed account of Virchow's so-called multilooular Echinococcus-growth — Its resemblance to CONTENTS. XV alveolar colloid — Relative frequency of hydatids in. particular organs— Results obtained by Rokitansky and Davaine — Cases recorded in EngUsh periodicals — Statistics — Statements of Krabbe and Schleisner — Diagnosis and treatment — Prevention ... P. 273—288 CHAPTER IX. — BoTHaiocEPHAWJs latus. General and specific characters of Bothriocephalus latus — Its geographical distribution — Anatomy and development — Investigations of Schubart, Knoch, and Leuokart, respecting the ciliated embryo — The adult worm occasionally found in dogs — Probable source whence the larvae are obtaiaed — Mode of egg-discharge — Leuck- art's account of a second species of Bothriocephalus infesting the human body. 289—300 CHAPTER X.— Nematoda. The Nematoda, or round worms infesting man — General and specific characters of Ascaris lumhricoides — Structure and development — ^Views of Czermak, Eberth, and Schneider — Experiments of Richter, Verloren, Davaine, and the Author — Practical considerations — Remarkable cases — Treatment 301 — 315 CHAPTER XI.— AscAMs mtstax. The Author's discovery of the occurrence of Ascaris mystax as a human parasite — General and specific characters — Vindication of the accuracy of the statements of Irish naturalists — Cases by Bellingham, Pickells, Scattergood, and Leuckart — Structure and development — General and specific characters of Trichocephalus dispar — Organization — Remarks on Filaria lentis and F. trachealis . . . 316 — 333 CHAPTER XII.— Trichina spiralis. General and specific characters of Trichina spirofos— Historical notice — Our knowledge of the structure, migrations, and development of Trichina, as gathered from the investigations of Owen, Bristowe and Rainey, Virchow, Leuckart, and Davaine — Medical importance of the subject — The flesh-worm epidemic, or so-caUed Trichi- niasis — Cause of its prevalence in particular localities — Gamgee's practical observa- tions — Value of the experimental method of research .... 334 — 355 XVI CONTENTS. CHAPTER Xin.— Stbongylus beonchiaiis. General and specific characters of Strongylus bronchialis and Emtrongylus gigas—Orgam- zation of the latter — Characters of Sclerostoma duodenale and Oxyuris vermicularis — Conflicting statements respecting the anatomical peculiarities of the Oxynrides— Opinions of Eberth, Kiichenmeister, "Walter, Schneider, Davaine, Claperede, and others — Development — Injurious effects on man — Treatment. . P- 356 — 372 OHAPTBB, XIV. — Dbacunculus mebinensis. Importance of the G-uinea-worm in reference to the disease termed dracontiasis — Principal authors who have written on this subject — General and specific characters of Dracunculus medinensis — Geographical distribution — Anatomical structure of the adult female — Organization and development of the embryos — Treatment and precautions to be observed — Summary — Brief notice of a second species. 373 — 389 PART III. SPUEIOUS HELMINTHOLOGY. OHAPTBK I. — Pentastoma TjBnioides. General and specific characters of Pentastema tcBnioides — Occurrence of this parasite in the human subject in its larval condition — Structure of the so-called Pentastoma denlimdatnm — How the eggs and embryos may gain access to our bodies — Pruner's discovery of a second species of human Pentastome— Its characters contrasted with those of the larva of Pentastoma ttenioides. 393 — 402 CHAPTER II.— Dactylius aculeatus. Probable identity of Dactylius aculeatus with MncJiytraus alhidms — The so-called Spirop- tera hominis referable to Filaria piscium — The Diplosoma crenatum or concrementa OONTENTS. XVll /[yjMy Aaiicti artificially prepared from the ovisacs of the cod and haddock — Gordius aquaiicus not a human helminth— Other spurious parasites — Various foreign bodies mistaken for Entozoa— Hope's list of insects and their larvaa reputed to have come from the human body — Bots received from Dr. Kli-k. . . . P. 403— 420 BIBLIOGRAPHY. List of Works, Memoirs, and CoTnmuTiications on the subject of Internal Parasites, which have appeared in the BngUsh language during the last half century. 421 DESCRIPTION OF PLATES. FRONTISPIECE. This plate represents two different examples of a large fluke {Fasciola gigantea, Cobbold) taken from the biliary ducts of the liver of a giraffe (x 2\ diam.). The specimen to the left has the anterior surface exposed, so as to display the oral and ventral suckers, and, more particularly, the dendriform digestive apparatus which has been injected from the mouth by artificially prepared ultra- marine. The figure to the right exhibits the dorsal aspect of the other specimen, show- ing, more especially, the multi-ramose character of the water- vascular system, the vessels of which have been distended with vermilion. The direction of the primary branches of the two canal-systems forms a complete contrast. The original preparations and drawings from which these figures have been taken, are in the author's possession. — T. S. C. PLATE II. 1. Eight examples of a small fluke (Distoma conjimctum, Cobbold) obtained from the Hver of an American red fox (Gcmis fulvus) ; the central pair being sexually united. Natural size. 2. One of the same, coloured to render the parts more distinct (x 35 diam.) ; a, oral sucker ; 6, acetabulum ; c, oesophageal bulb ; d, d, digestive canals ; e, reproductive papUla ; f, commencement of the uterus ; g, ovary, with two excretory ducts coming from the vitclligene, or yelk-forming glands ; h, h, primary branches from the main trunk of the water- vase alar system ; i, i, the viteUigenes ; Tc, h, testes ; I, contractile vesicle. 3. Group of ova. Slightly magnified. 4. Three of the same, showing the opercula, segmented yelks, and granular contents escaping from the lowermost specimen (x 150 diam.). 5. Mass of glittering corpuscles from the interior of the contractile vesicle (X 250 diam.). The above figures are from original sources. — T. S. C XX DESCRIPTION OF PLATES. PLATE III. via. 1. Sexually mature example oi Amphistoma com'cmot, magnified about 12 diam. It exhibits the oral aad caudal suckers, the intestinal ca3ca (coloured blue), the uterine canal (yellow), the nervous collar and so-called cerebral gan- glia, and, more particularly, the complicated system of water vessels (red). ■ — After Blanchard. 2. Another specimen (x 2 diam.) with the dorsal surface exposed.— Blanchard. 3. The same viewed laterally. — Blanchard. 4. Part of the female series of reproductive organs, isolated to show the connec- tion of the vitelligene glands with the ovary and with the uterus (x 12 diam.). — Altered from Blanchard. 5. Male reproductive organs (x 12 diam.).— Altered from Blanchard in accordance with an original dissection. 6. Egg of an Amphistoma taken from the paunch (rumen) of a zebu, formerly living in the Zoological Society's Menagerie, Eegent's Park (x about 80 diam.) . — Original. 7. Seminal corpuscles from the testis (highly magnified).— After Blanchard. PLATE IV. 1 and 2. Two examples of Oxyuris curimla from the large intestine of the horse. Females. Natural size. 3. Section of the anterior part of the body of one of the above, showing the fine transverse rings and conical form of the head. Slightly magnified. 4. Another view of part of the head, showing the oral aperture, the transverse striffi, and, more particularly, the elastic denticles (houppes de polls cm cirrh.es flottcmts of Dujardin) projecting from the pharynx (x 60 diam.). 5. An egg taken from the smaller of the two worms. Highly magnified. 6. Vegetable debris from the intestine canal of one of these Oxyures ; a, hair con- stricted at the base ; I, elongated epidermic cell ; c, oval parenchymatous cell ; d, e, simple unicellular hairs ; f, fringed epidermic cellular tissue ; g, spiral fibre. Highly magnified. These figures are copied from drawings executed by Mr. Busk. PLATE V. 1. Two examples of the whipworm {TrichooepJialus affinis, Rudolphi) from the coecum of a young giraffe which died in the Zoological Society's Menagerie, Regent's Park. The upper one a female, the lower a male. Slightly enlarged. 2. Head of the male specimen, showing the spurious winged appendages on either side of the mouth (x about 200 diam.). 3. Section of the neck : a, longitudinal band of epidermic cells ; a', four of the same isolated and seen under an altered focus J h, fold of the oesophagus- c, c, transverse strise; d, d, oval corpuscles (x 230 diam.). DESCRIPTION OF PLATES. xxi FIG. 4. Enlarged view of tlie spirally folded caudal extremity of the male Triclioce- phalus. 5. Part of the same, more highly magnified, to show, a, protrusor muscle ; b, cloacal aperture; c, sheath of the penis or appendix copulatorius (x 110 diam.). 6. Bxserted membranous vulva, showing the vaginal passage and retroverted spines (x 140 diam.). 7. Four unimpregnated ova (x 220 diam.). 8. Fully developed egg with a bisegmented yelk and highly refracting nuclei (x 180 diam.). These figures are original. — T. S. C. PLATE VI. 1. Head of a male specimen of Prosthecosacter convolutus (magnified 60 diam.), which measured fifteen lines in length. From the lungs of the common porpoise. The oesophagus and upper part of the intestinal tube are seen through the integument. 2. Caudal extremity of the same worm, showing the intromittent organ and accessory appendages. Viewed from behind (x about 60 diam.). 3. A more highly magnified representation of the tail of the male seen from the so- called ventral aspect. It exhibits the great lateral membranous appendages in their fully expanded condition, a small pair succeeding them, the terminal lobes surrounding (with their contained muscular organs) the cloacal orifice, the sheath of the penis, the double intromittent organ, and the lower part of the alimentary canal (^ 220 diam.). 4. Prosthecosacter convolutus. Female. Natural size. These figures are from drawings by Mr. Busk. PLATE VII. 1. Anterior extremity of a female example of Prosthecosacter convolutus (magni- fied 60 diam.). 2. Caudal extremity of the same, showing numerous embryos in the interior (x 60 diam.). 3. Another view of part of the same, showing the prominent lateral vesicle, the uterine canal, and a young embryo in the act of escaping per vaginam (X 220 diam.). 4. Section of the uterus, with contained ova in various stages of development (X 220 diam.). 5. One of the free embryos isolated (x 360 diam.). These figures are from drawings by Mr. Busk. PLATE VIII. ] . Section of the intestinal tube of the speckled salamander {Lissotriton punctatus), laid open to exhibit the mode of attachment of Echinorhynchus antJw.ris to the mucous surface. Natural size. XXU DESCRIPTION OP PLATES. PIS. 2. Male Eehinorhynchus anthuris (x 8 diam.). 3. A loose ovarian vesicle, containing germs in various stages of development. 4. A series of the germs isolated. 6. Another loose ovarian vesicle with its germ-contents rather more advanced. 6. Antero-posterior view of a folly-developed egg, enclosed in its primitive envelope. 7. Another example viewed laterally. 8. Ovum separated from its primitive envelope, showing the shell (chorion), and superfluous yelk mass still adherent. (The last six figs, x 350 diam.) 9. Several examples of HcJdnorhynchus angustains from the intestine of a trout. Natural size. 10. One of the same (x 12 diam.). 11. Uchinorhynchus nodulosus, from a small trout. Natural size. 12. The same (x 12 diam.). 18. Two eggs of-B. tiodulosus, showing their peculiar form and circumscribed yelk contents (x 1000 diam.). Figures 1 to 8 inclusive are from original sources (T. S. C), the remainder from drawings by Mr. Busk. PLATE IX. 1. Cyst from beneath the peritoneal surface of the intestine of a haddock. (Natu- ral size.) 2. The same ruptured (x 4 diam.). 3. Scolex of a Tetra/rhynchus escaped from the ruptured cyst, and showing the invaginated head and body (x 4 diam.). 4. The same, with the head and body drawn out. Natural size. 5. Part of the scolex, exhibiting four narrow phylloid bothria, the body part of the so-called caudal vesicle, and, more particularly, the four armed proboscides, two of which are partially protruded (x 20 diam.). 6. One of the calcareous particles from the caudal vesicle (x 200 diam.). 7. Section of a proboscis, showing the peculiar arrangement of the hooks and booklets. The figure marked e represents a series of delicate anasto- mosing canals seen beneath the integument at the lower part of the body in front of the caudal vesicle. These figures are original. — T. S. C. PLATE X. 1. Outline of the dissection of a young sun-fish {Orthagoriscus moZ«), showing several TebrarhyncM lodged within cysts imbedded in the retractor muscles of the anal fin. Reduced to one-sixth of the natural size. 2. The so-called head, neck, subcervical enlargement, and upper part of the body of TetrarhynoJius reptcms inclosed in its transparent sheath. Enlarged one- third. 8. Anterior fourth of the body of the same removed from its investing capsule. Natural size. DESCRIPTION OF PLATES. XXIU 4. A few articulations or sexually immature proglottides from tlio lower part of the body. Natural size. 6. One of the club-shaped proboscides isolated (x 20 diam.). 6. Diagram of one of the smaller hook-circles (x 60 diam.). 7. One of the Isacge hooks (x 260 diam.). 8. One of the small hooks (x 260 diam.). 9. Head oi TetrarTiynchm reptans viewed from above (x 8 diam.). These figures are original.- — T. S. C. PLATE XI. 1. A mature specimen of Fasciola Jiepatica seen from the ventral aspect (x 6 diam.). After Blanchard. 2. Diagram representing the digestive system (x 2 diam.). Original. 3. Diagram of the water-vasculaj system (x 2 diam.). Original. 4. Outline of the BO-caUed cerebral ganglia, commissural band, lateral ganglia, and branching filaments. Altered from Blanchard . 5. Diagramatic representation of a few of the cutaneous spines (highly magnified). Original. 6. Upper part of the male reproductive apparatus. Altered from Kiichenmeister. 7. Egg of Fagciola hepaiica, showing the so-called mulberry stage of yelk- segmentation. Original. PLATE XII. 1. Head, neck, and upper joints of Tcenia solium. Reduced from Blanchard. 2. One of the lower or sexually-mature joints of the same, showing the water- vascular canals and the branched uterine organ distended with ova. After Blanchard. 3. Two eggs ; one of them containing a six-hooked embryo. Original. 4. An egg invested by its primitive yelk-sac, the superfluous granular yelk-mass is also shown. Original. 5 — 10. Six dissections, showing the so-called Oysticercus cellulosa in various stages of development. Reduced from Leuckart. 11. A folly-developed Gysticereus cellulosw, taken from fresh pork. (Natural size.) From a fig^e by the late Professor Smith, of Cork. 12. Cysticercus from salted pork. After Smith. 13. The same (as Fig. 11), x 6 diam. Smith. 14. Head and body withdrawn from the caudal vesicle. Smith, 15. One of the cephalic hooks (x 400 diam.). Smith. 16. A group of the so-called calcareous particles (= " assimilating cellules," Smith) from a Cysticercus taken from salted pork (x 620 diam.). Smith. PLATE XIII. 1, Juvenile hydatid, about six weeks old (x 50 diam.). From a specimen reared by Leuckart, and now in the Author's collection. Original. XXIV DESCRIPTION OP PLATES. 2. Portion of a large hydatid from a cyst in the human liver. Part of a speci- men preserved in the Middlesex Hospital Museum. Dr. Murchison'a case. Coloured naturally by bile. Original. 3. Similar portion of another human hydatid, artificially coloured with magenta. Dr. Greenhow's case. Specimen preserved in the same museum. Original. 4. Scolex, or one of the Bchinococcus heads, showing, more particularly, the hooks, suckers, and calcareous particles. BVom a zebra (x about 500 diam.). After Huxley. 5. Two of the hooks separated ; one seen in profile, the other in front. Huxley. 6. An entire sexually mature Tania echinococcus, showing the head, with rostel- lum and suckers, and the three succeeding segments, the last of which contains the ova and other reproductive elements. The water-vascular system is likewise displayed. Outlined, with the aid of a camera, from a specimen prepared by Leuckart, and now preserved in the Author's collec- tion. (Magnified 30 diam.) Original. PLATE XIV. 1. A detached and flattened Echinococcus brood-capsule, showing the scolices in various stages of development, and their attachment, in situ. Taken from an hydatid found in the pig. — Busk. 2. An imperfectly developed scolex, from the same. — Busk. 3. One of the smaller hydatids, or so-called daughter vesicles in process of degeneration. The partially disintegrated scolices and separated hooks are seen in the interior. — Busk. PLATE XV. 1 . Group of Echinococci attached by their pedicles to a portion of the collapsed wall of a brood-capsule ; all the heads and cephalic hooks remaining inverted. From the hydatid of a sheep. — Busk. 2 — 7. Six scolices in various stages, separated from an hydatid occupying the human liver. They floated loosely in a bright yellow-coloured fluid, dis- tending the maternal cyst. — Busk. PLATE XVI. 1. A full-grown male specimen of Ascaris limibricoides ; showing, especially, the prominent mouth and double spiculum. Natural size. 2. Head of the same, exhibiting the form and position of the separate lobes of the lip (x 10 diam.) 3. Tail of the. male (x 10 diam.). 4. Tail of the female (x 10 diam.). 5. Vas deferens, seminal reservoir, and pouch for the spicules. Slightly enlarged from a dissection. 6. Uterus, uterine horns, and commencement of the oviducts. Slightly enlarged. The above figures are original. — T. S. C. DESCEIPTION 01^ PLATES. XXV PLATE XVII. PIG. 1. Nucleated germs fromthe coecal extremity of the ovarian tube otAscaris mystax. 2. Pedunculated ova at an early stage of development. 3. Two similar ova of a triangular form and further advanced. 4. TJnimpregnated ovum still further developed. 5. Ovum " duriug fertilization, whose vitellus is much broken up by the sper- matic particles." 6 — 17. Impregnated eggs in various stages of development during the process of yelk-segmentation. 18 — 24. Sumlar series, showing the finely granular yelk gradually developing itself into a vermiform embryo. The above figures are from Nelson ; beiug the same as those selected by Prof J. Hughes Bennett to illustrate his first Lecture " On Molecular Physiology," etc., published in the " Lancet," for Jan. 3rd, 1863. Figs. 1—3 are X 330 diam. ; the remainder x 220 diam. PLATE XVIII. Head of Oxyuris vermicularis, showing the exserted trilobular lip, the com- mencement of the pharynx, the transverse lines, and, more particularly, the lateral winged-appendages (X 220 diam.). Head, neck, and upper part of the body of the same, exhibiting the retracted mouth, the lateral alee, the transverse markings of the iutegiiment, and, more especially the pharynx, oesophagus, and upper part of the intestinal canal (x 220 diam.). Section of the body of the same, showing ova within the uterine canal, and the mode of termination of the vaginal passage (x 110 diam.). These figures are from drawings by Mr. Busk. PLATE XIX. 1. A female Oxyuris vermicularis, displaying the normal position of the digestive and reproductive organs, and the points at which their several outlets terminate (x 20 diam.). 2. Oral extremity of the same, showing the partly protruded lips, the lateral alee, and pharyngeal muscles (x 450 diam.). 3. Section from the lower part of the body, exhibiting the mode of termination of the intestinal canal, and, more particularly, numerous ova lodged within, in the folded extremity of one of the uterine horns (x 220 diam.). 4. Four ova ; a, showing the commencement of the embryonic formation, and h, c, d, the completed tadpole-shaped embryo in their interior (x 450 diam. ) . — Original. Figs. 1 to 3, inclusive, are from drawings by Mr. Busk. d XXVI DESCRIPTION OP PLATES. PLATE XX. 1. A female example of Dractmeulus medinensis of tlie natural size. 2. Caudal extremity of the same ; considerably magnified. 3. Enlarged view of the head, showing its truncate form and the position of the equidistantly situated cephalic papillEe ; magnified. 4. View representing the field of the microscope with numerous embryos in focus. Drawn with the aid of a camera (x 60 diam.). 5. One of the embryos naturally coiled upon itself (x 500 diam.). The above figures are original. — T. S. C. PLATE XXI. 1. A male example of Pentastoma tcenioides. Natural size. 2. A female specimen of the same worm. Natural size. 3. Upper fourth of the body of the so-called Pentastoma dentioulatum, showing the mouth, cephalic claws, integumentary spines, stigmata, and internal glandular parenchyma (x 60 diam.). 4. One of the claws isolated ; a, moveable hook ; b, tubular portion of the capsule ; c, longitudinal groove ; d, hood ; e, the three-cornered point-cover ; /, extensor, andy, retractor muscles of the hook (x 100 diam.). 5. Diagram of a portion of integument (with the spaces between the rows of hooks shortened) ; a, spines ; 6, stigmata (x 250 diam.). 6. Parenchymatous glandular cellules (x 220 diam.). 7. Egg of Pentastoma tcenioides, with its contained embryo. — Leuckart. 8. Embryo of the same after its escape from the egg. — Leuckart. Figs. 1 to 6, inclusive, are original. — T. S. 0. ERRATA. In the first sheet of this work, the scholar will readily notice the omission of several Grreek accents, as, for example, at page 1, in the words eXfjuvOt^, A.oyos, and evTOS, ^b)ov, Xoyos, for which read, IXfiwdti, Xdyos, and cvtos, i,Siov, X6yo f t r *: ■■ i'lGr. 12.— Gastekostoma geacilesceks, • Wagener j from the intestines of the Angler (Lophius piscatorms). X 60 diam. — Original. Gasterostoma. — In this singular genus the ventral sucker (Fig. 12) seems to have taken the position usually assigned to the oral opening, whilst the latter is placed low down towards the centre of the body. The digestive coeca also disappear, leaving GASTEEOSTOMA — AMPHISTOMA. 37 only a short stomachal cavity, which reminds one of the same viscus in the imperfectly organized sporocysts or redi^e. The yelk-forming glands exhibit conspicuous, round, secreting cells, the testes being also largely developed. I have also noticed two other small bodies, one of which probably represents the ovary or germstock, whilst the other may be referred to the recejj- tacuhtm seminis, or posterior seminal vesicle of Von Siebold. The connection between these several organs is not seen in this specimen, but their relative position is well shown. When the species first came under my observation, I naturally followed Rudolphi, who described this trematode as a distome {D. gracl- lescens, Eudolphi). I remember seekmg most diligently for the digestive tubes, being greatly -p-azzled^ not merely by then- absence, but also by the character and position of an organ which we now well know to be the sheath of the intromittent appendage. The uterus also terminates in its immediate vicinity, opening externally by a common outlet. The anatomy of this genus has been pretty fully illustrated by Von Siebold. According to Molin, the excretory, water- vascular organ (or respiratory apparatus, as he interrogatively puts it) consists (in Gasterostoma fimbriatum) of a broad central tube occupying the entire length of the body. In connection with this tube, he did not discover any branches, but he represents it as a simple sac opening externally at the caudal extremity. Amphistoma. — The most marked character in this genus has refer- ence to what may be styled the caudal position of the acetabulum, which is also very largely developed, being two or three times gi-eater than the oral sucker. This feature is admirably shown in the copy here given of Blanchard's enlarged figure of Amphis- toma conicwm (Plate III. Fig. 1), the same species being also represented by two other views where it is drawn twice the natural size (Figs. 2 and 3). The digestive system conforms closely to the true distome type, as do also the reproductive organs, both of the male (Fig. 5) and female (Fig. 4). The ova in this species are about l-150th of an inch long, and l-250th of an inch 38 ENTOZOA. in breadth. The egg represented in the accompanying plate (Fig. 6) was obtained from an amphistome found in the paunch of a Zebu formerly living in the London Zoological Society's Menagerie. Fig. 7 represents a group of sperm-cells or corpuscles from the testes. The latter organs, according to my own dissections, are not oval, but lobed, and, therefore, I have in this particular modified the otherwise generally accurate representation of Blanchard. But the most striking appearances in the accompanying illustration have reference to the pouched coecal ends of th^ minute twigs of the water- vascular system, which, if Blanchard' s drawings are correct, entitle him to the credit of having first pointed out such a mode of origin in these vessels. Dr. Guido Wagener has indicated a similar arrangement in connection with the water- vascular system in Holos- tomata, but my own recent inquiries enable me to assert most positively that no such enlargement of the ultimate ramifica- tions obtains in the genus Fasciola. The general arrangement of these vessels in the last-named genus is indicated in one of the figures given in the Frontispiece, but I reserve a more particular account of this system -until I specially treat of the anatomy of the common fluke in the Second Part of this work. In the meantime I would call attention to the differences observable in the arrange- ment of the vessels of Fasciola as compared with the same series of structures in Amphistoma. Long ago, Laurer pointed out the course pursued by the two main channels, from the head down- wards on either side of the body, and their ultimate communica- tion by means of a pyriform reservoir, as here shown on the dorsal surface of the Amphistome. Several authors, such as Bojanus, Diesing, Laurer, and Blanchard, have described a nervous system in this genus, and Laurer even aflBrmed that he had seen gangli- onic enlargements along the course of the principal nerve-trunks both here and in other trematodes. It is very doubtful, however, if any lateral gangha exist. The larvee of Amphistoma conicum have not yet been identified, but in all likelihood they dwell in the bodies of water-snails. This may be inferred from the circum- I-LAT HI. mi n^ -':;'^^,:V/-^ vv '-* ) . ^ ^ /vi:aritii'5tonia conLCum, K.udolpl:ii. ^f^i??' Blanchard. AMPHTSTOMA — ECHINOSTOMA. 39 stance that the larvae or cercarias of another species [AmpMstoma subclavatum) which, in the adult condition, dwells in frogs and newts, have been found both by Filippi of Turin and Pagen- stecher of Heidelberg, on the surface of the body of various species of Planorbis ; it would seem also, that Van Beneden has found them in different species of Gyclas. If this be correct, it becomes quite clear that when deer, sheep, or cattle resort to ponds and running streams to quench their thirst, they necessarily run the risk of infecting themselves with these larvae ; and in this way they are probably transferred to the paunch or rumen, where, becoming attached to the internal lining membrane of the organ, they com- plete their final stage of development. FjcMnostoma. — In this genus — or sub-genus, as originally established by Dujardin — ^the oral sucker is surrounded by a circle of little spines, or it occupies the centre of a disk which is cleft at the ventral or anterior aspect. In the latter case the disk is either bordered both laterally and above by spines, or there are two large, lobed appendages,, whose margins are furnished with spines. In other respects this genus very nearly corresponds with the typical distomes, but the simple digestive tube bifurcates immediately below the oesophageal bulb. As an illustration, I select the Echi- nostoma hispidim,, which species Dujardin — being misled by OrepHn's erroneous description — omitted to place in this genus, although he had previously entertained a very strong suspicion that it was a true echinostome. The specimen here drawn (Fig. 13) was taken by me from the spiral intestine of a sturgeon (1855), in which fish it occurs very abundantly. It will be noticed that there are two rows of large spines surrounding the cephahc disk, the latter structure being incomplete at the ventral margin (which is here turned away from the observer). The relative disparity of the two rows of cephalic spines are better seen in more highly magnified figures of these organs. The integumentary spines clothing the general surface of the body vary considerably in character, according to their position. Those situated at the 40 ENTOZOA. neck are narrow and sharply pointed, but, as regards size, they gradually dwindle down to a mere point or tubercle as our inspection approaches the caudal extremity, where, in point of fact. If* I'wi >ri iK' i. Fi&. 13.— ECHINOSTOMA HISMBOM, Cobbold ; ft'om the spiral intesHne of the Sturgeon (Acipemer X 15 diam. — Original. they become altogether obsolete. In the enlarged figure here given, we obtain a back view of the head and a lateral view of the body, the neck having been partially twisted ; the ventral sucker is concealed, but the semi-transparency of the skin permits a view TUTSTOMTD^!. 41 of the internal reproductive organs, which it is here unnecessary to particularize. TristomidcB. — The various members of this family display a leech-like aspect, in consequence of which they have been placed either along with the Malacobdellidce, or in some other allied family of the suctorial annelids. It is admitted, on all hands, that the tristomes are not entozoa in the literal acceptation of the term, yet it will be seen that their internal organization conforms more strictly to the trematode type than to that of the Hirudinidce. Thus, they support two small suckers anteriorly and one large sucker posteriorly, the body being externally smooth, devoid of annulations, and more or less compressed. The mouth is placed in front between the cephalic suckers, communicating with a beau- tiftdly ramified and dendriform intestine, whilst the main divisions of the latter, from either side, combine at the lower part of the body, so as to form a closed system of tubes. The tristomes have therefore no anus. In some species the large caudal sucker is sessile ; in others it is stalked or pedunculated, being in either case bordered by a membranous fold (Dujardin). AH the species are hermaphroditic, and display an arrangement of the reproductive organs very similar to that which we find to be present in the flukes, properly so called. These animals, as before implied, are ectozoa, some of them living on the gills of fishes, others attaching themselves to the general surface of the bodies of their piscine hosts, selecting especially the neighbourhood of the fins, whilst a third kind are parasitic on crustaceous parasites, the latter being also attached to marine fishes. Development. — Our knowledge of the genetic history, in so far as it relates to the typical members of this family, must be consi- dered very imperfect; but m the case of the aberrant genus Udonella, the mode of development is known to be remarkably simple and direct. In this genus, according to the researches of Van Beneden, the embryos are comparatively large, and they acquire the form and characteristics of their parents whilst they 42 ENTOZOA. are still witMn tlie egg- shell. Even before the period of their liberation, they exhibit all the essential organs of reproduction and alimentation, and are therefore ready to assume an independent existence the moment they quit the shell. The eggs themselves are oval, with a slight tendency to become pyriform, being a httle compressed laterally at one pole, where the chorion is prolonged into a single filamentary process, which may be aptly termed the " holdfast." Van Beneden suggestively compares a group of them to a "bouquet of vorticells." On quitting the shell the embryonic Udonella at once attaches itself to the Galigus, and in this situation continues to grow until it acquires the adult condition. The entire course of development is thus rendered extremely simple, and we are hereby confronted with the fact of a trematode worm passing through its life-cycle without the remotest indication of those phenomena of alternate generation which so commonly prevail amongst the true distomes,monostomes, and other digenetic fltikes. Genera.-^Tristoma, Cuvier; ^= NitzscMa, Yon Baer ; = Gap- sola, Bosc ; = Phylline, Oken ; Epibdella, Blainville ; Udonella, Johnston ; = Amphibothrium, Trey and Leuckart ; JEncotyllabe, Diesing ; Galicotyle, Diesing ; Benedenia, Diesing ; Notocotyle, Diesing. Polystomidce. — This family comprises a variety of remarkable genera characterized by their possessing in common several suckers which, for the most part, border the posterior extremity of the body ; but, in respect of form and general appearance, they are often widely dissimilar. I accept the family as an equivalent to Dujardin's first group of trematodes which he termed " Onchoboth- riens," rejecting only his genus Diporpa, since we aU know from Yon Siebold's researches that this form is a juvenile condition of Diplozoon. In this family Van Beneden includes the genera Galceostoma and Gyrodactylus, but I propose to place these singular organisms in a separate family. In all the Polystomes we have a more or less ramified intestine, but the reproductive organs conform POLYSTOMIDil!). -I'O to the general trematode type, exhibiting only certain departures in their mode of arrangement. All are hermaphroditic, the eggs being supplied with filamentary appendages, in some only at one pole of the shell, in others at both ends. The water- vascular system is conspicuously developed. AH the species are supplied with an armature of prehensile hooks, these horny structures being either connected with their complicated series of suckers, or else placed altogether independently apart, in which case they are usually situated in the central line of the body. In the sexually immature Diporpa-condition of the genus Diplozoon, there are two supernumerary hooks associated with a dorsal sucker at the centre of the body, and it is by means of these anomalously-placed organs that a conjugation between two such juvenile forms is effected. These two individuals become organically united for life, after the fashion of the Siamese twins ; and, according to the investigations of Yon Siebold, it is not until after this conjugation has been con- summated that the sexual organs make their appearance. In Onchotyle appendiculata we are presented with pecuHarities of form scarcely less remarkable. In this creature the lower end of the body suddenly merges into a curious appendage which is placed almost at a right angle with the body itself, and in this way, as Van Beneden justly remarks, the entire animal resembles a httle hammer; the resemblance being very much heightened by the circumstance that one end of the appendage is cleft so as to cor- respond, as it were, with the notch which we employ in the action of naU-drawing. At the bifurcate extremity of this singular taU Van Beneden describes the occurrence of two oval contractile vesicles. These organs open separately, one at either point, being also internally connected with the water- vascular system, which is consequently double in this genus. In point of function. Van Bene- den regards these vessels as uriniferous. A little above the pulsatile vesicles we find two recurved hooks, which are hkewise bifurcate at their base, and there are other prehensile elements occurring in connection with these suckers. Each one of these last-named 44 BNTOZOA. organs, of wHch there are six in all, supports a single scimitar-shaped homy piece designed to strengthen the sucking and grasping action of the disk ; and the latter organ consists of a strong, muscular, spherical cup, whose margins are capable of being folded some- what after the fashion of a double nightcap. As regards the visceral arrangements of this genus, it is unnecessary to enter into minute details, but I may briefly remark that the digestive coeca are rather irregularly ramose, whilst, in other respects, these organs conform to the general trematode type. The species here described was, in the first instance, discovered by Kuhn attached to the gills of a dog-fish (ScilUum catulus), but it has since been found as an ectoparasite upon other marine fishes. Its ova carry two filamentary "holdfasts," one at either extremity of the chorion. Genera. — Folystoma, Rudolphi ; = Hexacotyle, De la Roche ; = Plagiopeltis, Diesing ; = JBiexabothrivmi, Nordmann ; Pledano- phorus, Diesing; = Pledanocotyle, Diesing; Diclibothrium, Leuc- kart; = Hexacotyle, Nordmann; := Dvplohothrium, Leuckart; Solenocotyle, Diesing ; Octobothrmm, Leuckart ; = Placoplectanum, Diesing; = Odostoma, Kuhn; = Odopledanum, Diesing; = Mazocraes, Hermann; = Odocotyle, Diesing; = Dididophora, Diesing ; = Gydocotyle, Schultze ; = Discocotyle, Leuckart ; Axine, Abildgaard ; = Heter acanthus, Diesing ; Onchotyle, Diesing ; Diplozoon, Nordmann ; = Diporpa, Dujardin ; Gruhea, Diesing ; = Pleurocotylus, Gervais and Van Beneden ; Gotylaspis^ Leidy ; Aspi- docotyle, Diesing ; Aspidogaster, Von Baer. Gyrodadylidce. — As a fifth family of Trematoda, I here bring together those singular ectoparasitic creatures known as the Gy- rodactyles, along with an apparently closely allied genus to which Van Beneden has apphed the title Calceostoma. The Gyrodactyh have hitherto been classed with the Polystomidge, but one would think that the absence of several suckers would be alone sufficient to justify a separation. Amongst the characters which stand out most prominently are those having reference to the presence GYRODACTYIilD^. 45 of peculiar hooks projecting from the posteriorly- situated sucking disk. In the aberrant genus Galceostoma, this mechanism is reduced to a siQgle, though complex, horny structure placed at the margin of the caudal sucker in the central line, but in some of the Gyro- dactyli, the hooks are particularly numerous. As an intermediate type, I may iastance Gyrodadylus elegans, where the caudal sucker supports a pair of large laterally-recurved hooks, which are placed Fia. 14. — GrYEODACTTliTTS ELEGANS, Nordmann ; from the gills of Cyprinus hrama, showing an almost completely developed embryo in the interior ; a, a — oesophageal bulb ; g — testis ; h, h — posterior sucker ; i, i — the two large hoots ; k, le — the little marginal spines of the sucker. Highly magnified. — Van Beneden. back to back in the centre of the disk, being connected at then- upper or basal ends by the supervention of a transversely disposed median, semilunar portion. A series of tentacles serve to in- crease the prehensile action of the sucker. In many species 46 BNTOZOA. there are accessory horny developments in connexion ■with the male reproductive apparatus. The general organization of Gyrodactylus has been fuUy eluci- dated by Continental writers, and more especially by the indepen- dent investigations of JSTordmann, Siebold, Guido Wagener, Yan Beneden, and "Wedl, from whose combined experience we have, at length, arrived at the most satisfactory results. As "Wedl's conclusions are summarized within a small compass, I shaU here, instead of offering minute details of any one particular type, subscribe his final account of the principal characters of this group :* — a. " Oyrodadylus is found on the gills of fresh- water fishes under numerous specific forms, G. elegans being also found by Oreplin and Siebold on the fins. Moreover, as I have found nearly every species of fish supporting a particular gryodactyle-representative, it would seem that each finny creature supplies its own Gyrodactylus. Some- times two of them are parasitic upon the same giU, being fi'equently associated with Trichodince, as well as with the stUl unintelligible Psorospermice. ' ' b. " The clasping apparatus at the posterior end of the body must — in an animal so soft and constantly exposed to the passage of regular currents — be comparatively strongly developed and accommodated to the peculiar dwelling-places ; and probably the varying character of the latter supplies a reason why there should be so great a difference in the mechanism of the hooks belonging to the disk. c. " The hooked apparatus affords a very valuable and mathe- matically precise means of diagnosis in the determination of species. This differentiation may be accomplished by observing whether there are two or four large hooks ; whether there be one or two connecting portions, and by noticing their several forms and relations to one another ; and whether, again, there are hook- * Wedl, Prof. Dr. K. — Anatomische Beobachtungen ueber Trematoden, s. 34, efc seq., Wien, 1857. GYRODACTYIilDjE. 47 lets or not, remarking in the first instance their position, form, distribution, and so forth. d. "The integument is sometimes wrinkled transversely, at other times appearing to be smooth. e. " The muscular apparatus is, in certain cases, very strongly developed. In the majority of instances special muscles are inserted into the handles of the hooks, and they are also very fi-equently directed into the transverse muscles of the skin. In Oyrodadylus crassiusculus, we find a protrusor penis and retractor palparum medius. f. " Except in the case of G. elegans, four so-called eye spots are observed at the anterior extremity of all Gyrodactyli. As Siebold says, they answer the purpose of hght-refractuig organs. The palpi — ^which in G. crassiusculus are seen to contain muscular bundles — appear to be retractile touch- organs, extending more or less prominently forward. g. " Observations in regard to the alimentary canal are at present incomplete, for only in the case of Gyrodactylus cochlea did I find a single gullet demonstrable. This was furnished with epithelium, being tinged either yellow or brownish yeUow. It passed from before backwards, and was probably famished with an anus, whilst, in aU other instances, its passage could not be traced. The reason of this arises from the transparency of the intestinal con- tents, and fi^om the internal blending of the wall of the canals with the parenchymatous substance. The other organs also hinder our observation. h. " In three species of Gyrodactylus, namely, in G. cochlea, G. crassiusculus, and G. tenuis, the generative organs are thus disposed : — The vitelline organ is characterised by its botryoidal structure, and its round secretion-cells containing granular matter. These organs are so completely enveloped by a limiting mem- brane that there is no direct connexion between them and the oral sucker. The excretory duct lies in front of the ovary. In all the Gyrodactyli, where, generally speaking, one egg with its yellow 48 ENTOZOA. shell came under my observation, there was only this solitary example to be seen, and I only observed its escape on one occasion. The two seminal vesicles, standing out most conspicuously in G. tenuis, are filled by a convolution of filaments, and intercom- municate by a canal. The connexion of the posterior seminal vesicle with the presumed testes was not perceptible; but the anterior is in continuity with the external, horny, male repro- ductive apparatus. The last-named organ is characterized by much variety of form, so that one may exclaim, ' Ex pene speciem.' Speaking generally, we observe a peculiar, more or less curved penis, grooved for the passage of semen, and an accessory solid portion which is often hooked. The latter serves, probably, as a fang or organ for adhering to the vagina. In one instance where the accessory portion was absent, I found two hooMets at the entrance of the vagina. These, in all probability (functionally), represented the same, (being formed) for the purpose of laying hold of the penis when the latter was lodged within the sheath. Thus Qyrodactylus becomes sexually developed, and cannot be regarded merely as a kind of ' nurse.' " Development. — The genetic relations subsisting amongst the Gryrodactyles are in some respects peculiar, and have given rise to much controversy. We have abundant records of the principal facts and phenomena observed in the reproductive process, and, for the most part, there is little contrariety of opinion in regard to such data ; but, unfortunately, the method of interpreting these phenomena has, according to the source whence it has proceeded, produced a very variable result. Von Siebold, observing the sin- gular mode of reproduction as it takes place in Cfyrodactylus elegans, arrived at the conclusion that Gyrodactyles in general were only nurse-forms of some higher organism, and he pointed out, with undeniable accuracy, all the birth- stages of the young one as it apparently pullulated within the parent and subsequently emerged an almost perfect Gyrodactyle. Yon Siebold also remarked that the so-called " daughter," at the time of birth, nearly equalled the GYEQDAOTTI.IDiE. 49 " parent " in respect of size ; whilst, moreover, it contained within its interior another very young Gyrodactyle, or, in other words, a " grand-daughter." Professor Van Beneden, as we shall presently see, interpreted these facts very differently, but, it must also be noted that Von Siebold's ideas had gained a very general accept- ance. For my own part, I inchne to the views of Van Beneden ; but provisionally accepting Von Siebold's conclusions — so far, at least, as G. elegans is concerned — I may proceed to remark that I also have noticed the second generation, or daughter, to contain in its interior evidences of what I, at the time, supposed to be a third generation.* This phenomenon I observed in specimens of the worm obtained from the tails of Gasterostei caught in the Serpen- tine, Regent's Park. Indications of the third progeny were seen whilst the daughter still resided within the body of the nurse-parent, but the so-called grand-daughter acquired much greater conspiouity immediately after birth. In one instance, I had a very satisfactory opportunity of watching the process of separation. The " daughter" commenced showing itself externally by a slight bulging at the centre of the body of the parent, whilst the integument of the latter yielded on all sides of the bud-hke projection, and in such a manner as to convey the idea of a vaginal opening, although a sheath of this kind ■was by no means actually visible. There was an evident struggle on the part of the young one to free itself from the so-called parental envelope, but the tissues exhibited no evidence of injm-y. On partial protrusion, it was seen that the budding portion corre- sponded with the centre of the daughter's body, and this, in a little while, assumed the aspect of a semi- circular, or horseshoe- shaped, band. Subsequently the upper or anterior end became detached, the freed extremity being now recognized as the head, characterized by the possession of two ventricose lobes. A considerable interval elapsed before the broad posterior end of the animal could be dis- engaged, but immediately after this was effected the sides of the * As stated in my paper on Gyrodactyhis in the " Microscopical Journal," new series, vol. ii., p. 36, 18G2.--T. S. 0. H 50 ENTOZOA. parental envelope closed in upon the opening, and all that remained was a small cavity or sac, indicating the position recently occupied by the " daughter " Gyrodactylus. Altogether, the process occu- pied about five minutes from the commencement of the "budding" to the closure of the assumed vaginal outlet. In this instance I carefully compared the so-called "parent" with the "daughter," but in regard to size I can scarcely aver that the former was the larger of the two. The similarity of bulk is, perhaps, more apparent than real, owing to the circumstance that the freed young one rapidly extends itself and moves about in all directions, whilst the parent as readily contracts, or " shuts up," so to speak, thus appearing at a striking disadvantage. As I have before hinted, Yan Beneden demurs altogether to the relational view of these creatures estabhshed by Von Siebold. He does not admit the parent to be a kind of "nurse;" he does not consider the primary young one to be a "daughter;" and, conse- quently, he does not regard the embryo seen within the latter as a "grand-daughter." Yan Beneden, whose words I translate lite- rally, writes as follows :* — " According to our researches there is here a false interpretation ; the little daughter is lodged within the side of its pretended mother, and not in its interior ; instead of being its mother, it is its sister ; there is a difference of shape, because there is a difference of age ; the Gyrodactyles are vivipa- rous, and as among the higher Trematodes the eggs are formed one by one, one embryo is scarcely formed when another com- mences its evolution, and the egg-deposition is effected even whilst the embryo is being produced. The Gyrodactyles are therefore viviparous worms which beget a single embryo at a time, as those of the trematode group to which they are allied beget a single egg at a time ; and before the first embryo is expelled another is already partly developed. There, we believe, lies the correct interpreta- tion of that phenomenon ; instead of a bud it is an embryo, which has escaped from an egg. Here, therefore, we have no phenome- * " Memoire sui- les Vers Intestineaux." — Paris, 1868, p. 66. GYRODACTYLID^. 51 non of alternate generation or of digenesis, as Von Siebold supposes, but a simple viviparous reproduction." Genera. — Gyrodactylus, Nordmann ; Dactylogyrus, Diesing ; Galceostoma, Van Beneden; Tetraonchus, Diesing ; Diplectanum, Diesing. 52 ENTOZOA. CHAPTER IV. NEMATODA. The order of round worms, or Nematoda — Aspect, habits, and distribution — Probable number of known species — Classification — Anguillulidae — The common vinegar eel as a type — Genera — Gordudse, or family of hair-worms — Dujardin's account of the structure of Mermis niffreseens — The views of Meissner, Von Siebold, and Van Beneden respecting the development of Mermis— Genera — Structure of Sphseru- laria — Oxyurida, or thread-worms — Organization of Oxyuris curvula — Genera. In the foregoing chapters I have devoted as much space as could be spared for a general description of the sterelminthic group of worms ; and, therefore, I now pass to the consideration of the third order of helminths, or, in other words, to the Nematoda. This order is, as we have seen, equivalent to the second sub-class or ccelel- minths, in which the internal organs are loosely suspended within a weU. defined perivisceral cavity. The term Nematoda (z''J7^a-e2So9) implies the possession of a more or less thread-like form of body, but, in conformity with the most obvious and general character presented by nearly every member of the group, these helminths are with greater frequency denominated rownd worms. So far as I am aware, all the forms (except that of a new genus — Simondsia, T. S. C.) are very much longer than they are broad, and it is only in a few exceptional cases that we find a tendency towards the flattened character seen in other helminthic types. Aspect. — The Nematodes as a whole, and especially the more typical and better known forms, bear a marked external resem- blance to the common earthworm ; but their internal organization, when compared with that of the latter, will be found to differ most materially. The majority of the species are of small size, varying NEMATODA. 53 usually from a few lines to two or three inches in length ; how- ever, there are some exceptionally large individuals whose lon- gitudinal admeasurement extends to several feet. Cogent examples of this kind may be instanced in the great, red-coloured, kidney- worm (Eiostrongylus gigas) , in the large round- worm of the horse (Ascaris megalocephala) , and in the guinea- worm (Dracunculus medinensis) of tropical countries. Habits. — Most of the Nematoda are parasitic only during a portion of their life-time, though it must be allowed, as a rule, that the period of their non-parasitic existence is comparatively limited. Some few are altogether non-parasitic. In the case of those round-worms which expel their ova in a very imperfectly developed condition, a long immersion of the eggs in water appears to be necessary for the development of the embryo. In such cases the time of their non-parasitic condition will vary from six to twelve months, or even more. After this period, if they are not soon passively transferred to their proper hosts, they will, in aU likelihood, rapidly perish. Even in the case of the armed embryos of Mermis, the continuance of life is probably dependant on the success which attends their efforts to bore their way into the bodies of the hosts — grubs and caterpillars — which are suitable to them. In the Nematodes, therefore, larval migration is necessary for the welfare and continuation of the species, and this " wander- iQg," as it is called, may be accomphshed either in an active or in a passive manner. Distribution.— 'Nematodes infest abundantly the human body; they are scarcely less numerous in the higher apes and monkeys, being also tolerably frequent in the bats. Almost always present m the carnivora, we find them especially common in cats, dogs, and weasels. No less than six species, referable to four distinct genera, are described as infesting the hedgehog, not a few also occurring in the allied moles and shrews. In rats, mice, squirrels, rabbits, hares, and other rodents, they are equally abundant. Some few species have been found in the edentates, but they are 54 ENTOZOA. much, more prevalent in swine and their allies. In herbivorous animals, generally, they are common, being remarkably numerous in the horse, ass, ox, deer, and sheep. One or two species are constantly present in the seal and porpoise respectively, but we are very imperfectly informed as to their presence or absence in the large cetacea. The Nematodes, as a group, are particularly liable to invade aU kinds of birds, especially game and poultry. In reptiles they are certainly less numerous; but in fisbes they are almost as prevalent as in the feathered tribe. On the whole, therefore, it may be affirmed that, in so far as reference is made to the vertebrate host, the nematode species are more generally, numerously, and uniformly distributed than the individual members of other helminthic orders. Number and Arrangement.- — It is more difficult to arrive at an approximatively true estimate of the total number of nematode species in existence, than it is to form a similar estimate in regard to the other kinds of helminths. This arises first fi:"om the cir- cumstance that the forms are undoubtedly more numerous and more widely distributed ; secondly, because a multitude of juvenile forms have been taken for adults ; and thirdly, because the re- putedly distinct forms are less markedly definable than are those belonging to other orders of parasites. Altogether, nearly 800 species have been either described or indicated, but at the very lowest estimate I should think that not less than 250 of these so- caUed species might be legitimately cast aside as spurious. This very necessary deletion permits us to assume that the order of Nema- todes, "as at present known, comprises about 550 species. The various forms, naturally grouped, may be classed in the following manner :• — AnguilluUdos (Family I.) Gordiid skin to which they are attached be gently raised by means of the forceps it will be foimd to consist of two layers, an outer, thin, transparent cuticle (epidermis), and an inner, dense, fibrous cutis vera. The spines are often very loosely connected to the surface of the former, and in old specimens they are sometimes almost entirely wanting ; at aU times, they are more strongly developed anteriorly than in the caudal region. This is the case with most of the other armed trematodes. * In the " Boston Medical and Surgical Journal," for the years 1852-53-54, Dr. J. X. Ghabert has described several cases of Taenia, and it is averred that the tape- worms were associated with numerous specimens of Distoma hepaticum. The passage of distomes by patients duriag life is even regarded by Dr. Ghabert as indicative of the presence of Tccnia within the intestines. Surely Dr. Ghabert must be mistaken. Are not these so-caUed distomes the well-known proglottides f Not wishing to doubt Dr. Ghabert's statements, but, on the other hand, desirous of verifying the accuracy of the facts placed on record, I wrote (March 22nd, 1864) to Dr. Ghabert (at his residence, 431^, Grand Street, New York, U.S.) to request the favour of the possession of one of the specimens. Up to the present time, however (June, 1864), I have not been fortunate enough to receive a reply. In the " Gase of Tsenia" in a boy four and a half years old, given in the 49th vol. of the Journal, Dr. Ghabert writes as follows : — " In consequence of his passing the Distoma hepaticum, I concluded he must be aflQicted with TEenia." Further on it is added, that the administration of an astringent injection " caused the dis- charge of innumerable small worms (Distoma hepaticum,)." Gan anything be mofe decisive than this ? No helminthologist, past or present, ever recorded such a case. — T. S. G. FASCIOLA HEPATICA. 151 Beneath the skin are found numerous bands of muscular fibres, in which four separate groups may be recognized more or less dis- tinctly. They have been described as so many layers, but they are not readily separable from one another. Well-marked longitudinal and transverse fibres may be seen at all parts of the body, and two series of diagonally directed fibres, some passing downwards from right to left, and others from left to right. The fibres themselves belong, of course, to the non- striated kind of muscle, and consist of narrow, fiisiform cells, measuring from a, to 4 of an inch in length, and having a breadth of about the ^ of an inch. They are flattened throughout, and display a single oval nucleus, which refracts light rather strongly. Towards the anterior end of the body all the groups of muscular fibres are more strongly developed. The general parenchyma of the fluke consists of rather loosely- connected and irregular polygonal cells of unusually large size, measuring from J, to Si of an inch in their greatest diameter (Leuckart). The margins are well defined, and there is a distinct nucleus (dm " to ^") presenting a finely granular appearance. A clear, transparent, homogeneous fluid occupies the interior of the cells. AH the tissues of the body possess highly contractile properties, but the fluke is undoubtedly aided in locomotion both by the oral and ventral sucker. These organs may be regarded as specialized developments of the transverse and longitudinal system of fibres, which have become exaggerated to serve a distinct purpose. The oral sucker is perforated in the centre, and communicates with the oesophagus, but the ventral is imperforate, consisting simply of a cup-shaped disk, forming a sort of alveolus with a thick, circular, prominent margin. In both, two distinct sets of fibres are distin- guishable, that is, a circular series and a radial group. These bundles interlace one another, forming powerful sphincters, which, when apphed to any soft surface, must, during full action, produce a very considerable vacuum in the centre of the disk. The oral sucker difiers only from the ventral in respect of size and incom- pleteness at the lower part, in which latter situation it is either 152 ENTOZOA,. connected witli or prolonged into a series of fibres forming the so- called pharynx. As far as my own observations extend this special muscular development corresponds "with the cesophageal bulb, which in other trematode species is often entirely removed from its con- nection with the oral sucker, and consists of two sets of fibres as obtains in the sucker itself. Mr. Simonds, however, only recogni^ies one set of fibres, and says that " these fibres run lengthways by the side of the (oesophageal) tube, reaching from its upper to its lower part, and so embracing it as to form an elongated sphincter." My own observations appear to be borne out by the independent and earlier inquiries of Mr. Busk, from whose drawings the accom- panying figure is selected. The sucker here figured is taken from Fi&. 33.— The oral sucker of a small species of fluke (x 220 diam.).— Busk. a different species of trematode, but in all essential features it is the same as that of Fasdola hepatica. The radial fibres when viewed fi:'om above display a cellular appearance, the individual fibres being seen, as it were, in transverse section. As before remarked, these suckers are both employed as organs of locomotion, but the lower one also undoubtedly serves, as an anchor or holdfast. The oral disk will also materially assist as a prehensile organ for taking in the biliary secretion on which the animal feeds, whilst the pharyngeal sphincter wiU, as Simonds ■l.ATE XT. ) 1 (••f .J»-'i'i|l. lip 'i^' ; m -1 i> i^ I?' ^n"^ m- m ;K' l^fite v4 \"l ,/v^y^^ ^1^ 5H ?^^ 'k KaaCLOla Depat.ica LniueE'Us ,-l/;£T BlriHvhard. PASOIOLA HEPATICA. 163 believes, serve to prevent the regurgitation of the food after it has distended the stomachal passages. All who have had much to do with fresh living flukes must have observed a tendency to eject the stomachal contents, immediately on their removal from the liver of their host. The cold air — ^like the more cruel stimulus of salt applied to the skin of a recently gorged leech — causes the body of the fluke to contract and curl upon itself, and the animal pro- bably derives some relief by allowing the food to escape by the oral outlet. Mention of these phenomena naturally lead to the consideration of the digestive system. The mouth, as we have seen, is placed at the apical or lower part of the cup-shaped cavity of the anterior sucker. In this situation it leads into a comparatively short oesophagus (about i|g" in diameter) which subdivides into two primary intestinal divisions, the point of bifurcation being situated immediately above the location of the external reproductive orifices. The two primary digestive tubes run downwards in a parallel manner on either side of the central line, until they reach the caudal extremity. During their passage downwards they give ofi" a variable number of secondary tubes, which likewise in their turn give ofi" others, which subdivide, more or less frequently, when at length all of the branches ultimately terminate in blind coecal extremities (Plate XI., Fig. 2). A few short twigs are also given off" from the primary straight tubes, being directed towards the middle line, where they terminate very abruptly, but frequently giving evidences of an effort, as it were, on their part to develop tertiary tubes. In the region of the head and neck, the secondary branches are directed upwards and outwards ; lower down they diverge more directly outwards, whilst at the middle and lower part of the body they slant obhquely downwards toward the lateral borders. Alto- gether they form a beautiful series of dendritically ramifying canals, preserving on either side a tolerable, but not entirely uniform, degree of regularity ; moreover, the two halves of the system do not completely correspond, or, in other words, the 154 ENTOZOA. symmetry is not extended beyond the general disposition of the main branches. In no case have I witnessed any intestinal anas- tomoses. Several observers have represented the secondary and tertiary branches as becoming smaller and smaller as they proceed towards the margin, also conveying the idea, that the ultimate branchlets are extremely fine. This is decidedly an error, and shows that their descriptions have not been taken jfrom artificially injected specimens. The truth is, that the ultimate branches, as well as their ccecal ends, are only a very httle smaller than the primary intestinal trunks. Histiologically speaking, the alimentary tubes consist of two layers ; an outer fibrous wall made up of thin filaments, and an inner, cellular layer, consisting of columnar ceUules, which, when viewed in fii-ont, present a polyhedral figure. According to Leuckart, they have a breadth of i^ of an inch. The fluid intes- tinal contents are, for the most part, made up of bile derived from the gall ducts of the host, in which there may also be frequently observed numerous epithelial scales as well as blood corpuscles derived from the same source. These matters are therefore, mani- festly, the principal source of nutriment by which the fluke is supported ; but it is also probable that other nutrient fluids, absorbed by the skin, contribute their quota towards the growth and nourishment of the animal. In strong contrast to the digestive system of canals, there is another series of tubes lying in closer proximity to the dorsal surface of the body, and presenting features altogether distinctive. I here speak of the so-called aquiferous or water-vascular system. In favourable examples of the worm, every p^t of this set of vessels may be viewed by the aid of a pocket lens, even in cases where there has been no attempt made to inject them. In such examples I find one central, longitudinal trunk (^" broad), extend- ing backwards from the upper third of the body in a direct line to the extremity of the tail, at which point it terminates in an open foramen caudate (Plate XI., Fig. 3). At the spot coinciding with an imaginary line marking the upper third of the body, the single FASOIOLA HBPATICA. 155 main trunk divides into three branches, two of which approacli the ventral surface, sHghtly diverge and pass forward towards the head, whilst the third is continued on the dorsal surface in the middle Ime, forming, as it were, a continuation of the main trunk. This branch, however, is the most feebly developed of the three. During its coin-se upwards towards the head, the main trunk gives off a variable number of main primary branches, all of which are directed diagonally upwards and forwards ; and besides these, there are many smaller primary branches intercalated, as it were, between Fia. 34. — ^Mode of termmation of the coeoa of the so-called excretory or water- vaBCular system of canals in Fasciola hepatica (X 40 diam.). Outlined with the aid of a camera. — Original. the larger primary vessels. At a short distance from the central line, these vascular branches freely anastomose by the intervention of secondary and tertiary branches, and also by intermediary twigs, which cannot be said to be referable to one main branch more than another. Some of the non-anastomosing ultimate twigs, which are very numerous, are directed towards the dorsal surface, where they terminate in coecal extremities immediately below the muscular layers, whilst others are continued towards the lateral margins, where they also terminate in a similar manner. Under the half- 156 ENTOZOA. incli objective the precise mode of their final distribution is readily seen. The ultimate twigs lose that rigid, straight, tubular character which the primary trunks display, and twist somewhat irregularly, hke the mycelium of a fiingus. The final division is almost invariably bifurcate, in which case, however, there is frequently much disparity as regards the relative length of the divisions. In the foregoing woodcut, these appearances are correctly given [a, a, Fig. 34). The coecal extremities are always separated fi'om one another by an interspace more or less consider- able, and the final twigs often appear to have gone out of their way, as it were, in order to avoid the contingency of union. They seem to say " union is impossible," and bend suddenly upon them- selves, at an acute angle, to get out of the way of opposing vessels coming fi^om other directions {b, h, Fig. 34). Having succeeded with my injections of the water-vascular system in numerous instances, I am in a position to speak pretty confidently in regard to many of those points which have hitherto been regarded as doubtful. It is quite clear that the ancient view of Mehlis, as to the termination of this system by a caudal outlet, is correct ; but it is not quite so evident that the ultimate coecal ends of the excretory vessels have any connection with the so- called calcareous corpuscles. These bodies, indeed, do not appear to have any existence in the common fluke and its allies, although they have been found so abundant by Wagener in the trematode Holostomata. Possibly they may occur here in a very rudimentary or incomplete state ; but if we subject any one of the ultimate ccBcal ends of these vessels to high magnifying powers, we invari- ably find (in the fresh condition) the extremity of the tube occupied by a quantity of highly refi^acting yellowish corpuscles (the largest measuring j^") 5 looking very like fat globules. It is difficult to see any connection between these bodies and the calcareous corpuscles, especially as they do not exhibit the same phenomena under the addition of acid reagents. These highly refracting corpuscles vary very much in size, some of them, according to Leuckart, PASCIOLA HEPATICA. 157 attaining a diameter of 3^". I find the larger ones to measure fully 3-^3". In addition to these corpuscles, the vessels include a more or less abundant, transparent, watery fluid, in which the above- =S5 Fi&. 35. — Closed extremity of a water-vessel in Fasciola hepatica (x 260 diam.). — Original. mentioned bodies float freely. It is not improbable that the ducts contain vibratfle ciUa, but I am not aware that they have been actually demonstrated in Fasciola, although they have been seen in the excretory system of other entozoa. The walls of the vessels, according to my own observation, consist of a single layer of transparent polygonal cells, specialised apparently from the ordinary parenchyma of the body. Certainly this excretory system cannot be regarded as a true circulatory apparatus, for the median trunk is totally unlike the contractile dorsal vessel of leeches and other annehds. A true blood-system is entirely wanting. Besides the foregoing structures, Leuckart mentions the occurrence of another set of organs, which he calls cutaneous glands. They form a thick layer of cells with granular contents, varying fromT^o" to ^' in breadth, and having a distinct, bright nucleus measuring -wri' iu diameter. This layer is freely traversed by the terminal twigs of the aquiferous system, with which Leuckart thinks they may have some connection, although this union could not be actually demonstrated. The most important, however, of aU the internal organs of the hermaphroditic liver fluke are those concerned in the reproductive 158 ENTOZOA. process. The outlets of these organs are placed side by side, in the middle hne, and a little above the ventral sucker ; the male apparatus terminating externally by a conspicuous intromittent organ or penis. This appendage is very commonly found pro- truded in the dead fluke, being always, in this case, more or leas curved upon itself in a spiral manner. The organ itself consists of layers of longitudinal and transverse muscular fibres, surrounding a central mass of highly contractile parenchymatous cellules. Its extremity is lobed and imperforate, the included seminal duct (ductus ejaculatorms) terminating, accordiag to Simonds, on its surface, near a point corresponding with the commencement of the lower third of the organ. Not having myself seen the alleged opening at the extremity of the organ, I am inclined to beheve that Mr. Simonds' description of the generative appendage is, in this particular, more correct than any other that has appeared. In the retracted condition the penis is lodged within a distinct pouch or sac, its position being indicated only by a triangular depression and slight fiilness of the surrounding parts. The integument of the penis is manifestly a production of the ordinary epidermis and cuticular covering, and like the latter is furnished with a number of minute spines. These frequently drop off", causing the organ to appear naked. The pouch or citrhus-sac not only encloses a penis, during its retractation, but also a large flask-shaped seminal receptacle, in which, one may observe a dense granular mass, consisting of multitudes of spermatozoa. At the lower part of the sac the receptaculum seminis receives the two vasa deferentia, which combine to form a single channel near their point of junction with the receptacle (Plate XI., Fig. 6). These filamentary ducts are of unequal length, and distinct throughout the greater part of their course, which commences, in either case, at a point where the seminiferous tubes of the testes coalesce. In this animal the testes are exceedingly peculiar ; for instead of forming two large globular masses (as usually happens in the flukes), they are split up, as it were, into a multitude of very narrow vermiform tubes, being FASCIOLA HEPATICA. 159 spread out so as to occupy at least one half of the interior of the animal. The female organs are not less complicated. The vaginal outlet is placed a httle to the left of the middle line, immediately above the margin of the ventral sucker. According to Kuchenmeister, it has a common opening with the penis, but this error has been corrected by Simonds, and even by Kuchenmeister himself in a passage which he quotes from Mehlis. The vagina is probably capable of very great dilation, but in its ordinary condition it is much narrower than the extremity of the intromittent organ ; the aperture is so narrow, indeed, that it appears to be only capable of giving exit to a single ovum at a time. At a short distance from the orifice it widens out to form the true uterus, or uterine canal, which here consists of a long tube coiled upon itself, and containing in its interior a large number of brownish yellow eggs. From the ventral aspect this folded tube is easUy recognized by the naked eye, forming a conspicuous brown-coloured rosette, which is placed directly below and behind the ventral sucker. Towards the vaginal end the uterine tube looks more highly coloured than at its ovid^cal extremity, in consequence of the contained eggs being more completely developed in this situation. This is owing also to the circumstance that great numbers of the eggs are collected together at one spot, distending the tube very considerably. The breadth of the canal will thus be found to vary from -^" to ^" in transverse diameter. Towards the ovarian end of the canal the uterus becomes rather suddenly narrowed into a short oviduct, in which the eggs are seen lying, incompletely developed and very pale-coloured. This duct communicates in front with the ovary, a heart-shaped organ, which receives at its broad or lower end the united extremities of two other ducts, which meet and anastomose at this point. These two ducts are the primary, main, vitelhgene canals, and, from their dark-coloured contents, are usually very well marked and visible to the naked eye. They form together a continuous transverse line of demarcation, which 160 ENTOZOA. somewliat roughly indicates the limits of the superior third of the body. In some instances, one or other of these tubes is bifurcated at some part of its course, but usually both of them pass in a straight line to a point corresponding with the limiting border of the testicvilar filaments, one to the right and the other to the left. In this situation they divide abruptly into two secondary channels, which also, on their part, each form a continuous line, placed at right angles with the primary canal, and parallel with the lateral margins of the body of the animal. Throughout their entire course the secondary canals give off" tertiary branches, which pass outwards at a right angle to the former, and these again subdivide into minute twigs, which ultimately terminate in bundles of grape-like coecal extremities. These enlarged globular ends constitute the so-called yelk-sacs, and all of them, combined together, form the vitelligene glands which extend backwards from the anterior part of the body — on a line with the ventral sucker — to the caudal extremity. As shown in the drawing (Plate XI., Fig. 1) they form a brownish-coloured horseshoe-shaped mass, completely embracing the reproductive organs, and filling up the central space of the lower third of the body, where the latter is not occupied by the testes. In this situation the two vitel- ligene masses do not coalesce, but are separated from each other, in the middle line, by a very narrow space set apart for the passage of the main canal of the water-vascular system. The yelk-sacs themselves form little dots barely visible to the naked eye, from its" to ^o", and contaiu in their interior numerous yelk- globules, or nucleated cellules, measuring about the -3^ of an inch in diameter, the nucleus being ws". A nervous system has been described by Mehlis, Blanchard, and especially by Leuckart. It consists, firstly, of a pair of cephahc ganglia, situated in the space between the oral sucker and the pharynx, but separated from the latter by a thin layer of connective tissue. The gangha give ofi" two main branches or lateral nerves, which run downwards in a parallel manner, FASCIOLA HEPATICA. 161 near tlie middle line of the body, and give off secondary branches to the sides of the animal. According to Leuckart, the lateral gangha described by Blanchard do not exist. The cephalic ganglia, however, give off branches to the oral sucker and sides of the head, some of these twigs being probably concerned with the sense of touch. A thin, commisural filament connects the two gangha above the pharynx, but throughout the rest of the system the two divisions remain distinct. Comparison with Fasciola gigantea. — Before proceeding to the consideration of the eggs and the development of their contents into the embryonic and higher larval trematode conditions, I would direct attention to the differences subsisting between the common liver-fluke and a similar alhed form which I discovered some years since in the hver of a giraffe. Two examples of the species in question are represented in the frontispiece.* If the actual appearances presented by the water- vascular and digestive systems, respectively, in the frontispiece be compared with the diagrammatic representation of the same systems given,ia figs. 2 and 3 of Plate XI., it will be seen that they correspond in the main, but in the fluke fi:'om the giraffe the number of secondary branches rising from the central longitudinal main stems are, in either system, more numerous than obtains in the common fluke. Moreover, independent of the remarkable disparity of size, some of the specimens of Fasciola gigantea being fully three inches long, the relative form of the two species is very different. In aU the examples of F. hepatica the lower half of the body is gradually narrowed towards the caudal point, presenting a more or less V-shaped outhne, whilst in F. gigantea the narrowing only commences at a very short distance from the tail end, which in some instances is not only not pointed, but bluntly curved, or even truncated. In certain cases, the posi- tion of the /oramew caudale is significantly marked by a notch at * The left-hand figiire represents the digestive system injected with artificially pre- pared ultra-marine ; that on the right displaying the water-vascular system injected with vermilion. These drawings are from preparations in the author's possession. 162 BNTOZOA. or near the centre of the termination of the tail. Many other minor differences exist, which it is unnecessary to insist upon, especially as they are, in the main, dependent upon those already referred to ; but sufficient has, I think, been advanced to show that the notion entertained by Yan Beneden, namely, that these two forms are specifically identical, is incorrect. In this view, I am glad to find I have the support of so discriminating an authority as Leuckart, who arrived at the same conclusion fi?om an examination of two specimens which were much smaller than those fi'om which the figures in the frontispiece have been taken.* Special Structures. — Before passing to the consideration of the development of the common fluke, I may refer to one or two other structural pecuharities which I have hitherto omitted to mention. In addition to the cutaneous system of glands, Leuckart mentions the occurrence of a few equally distinct isolated gland-elements in the neighbourhood of the pharynx, as well as others imbedded be- tween the muscles of the pharynx and also between the muscles of the oral sucker. The cells are filled with coarsely-granular con- tents, and also display a highly refi:"acting nucleus. They are thought to possess a salivary function. According to the same authority, there is also a separate, thin-waUed, muscular sac, form- ing a distinct and independent organ, though intimately connected with the true pharynx. It appears to be a sort of diverticulum, for Leuckart has occasionally seen it filled with the ordinary intes- tinal contents. As a sohtary sac, it appears to be pecuhar to Fasciola hepatica, but Pagenstecher and Walter have described two * Without mentioning my name, MM. Panl Gervais and P. J. Van Beneden make tlie foUowing strange statement in their "Zoologie Medicale," Tom. ii., p. 201, Paris, 1858): — "Le Distome trouvS, en Europe, dans le foie d'une Girafe, et qui a ete decrit oomme une autre espece, n'est aussi qu'un Distoma hepatieum." As a " set off" against this, it is only due to myself to add Leuckart's comment (" Die Mensohlichen Parasiten. Erster Band." Lief. 3, s. 630), which stands .as follows : — " Das von Spencer Cobbold aus den GaUengangen de Giraffe beschriebene Dist. giganteum, das ich duroh die Freundliohkeit seines Entdeckers in zwei Bxemplaren untersuchen konnte, ist in der That eine eigene Species und keineswegs, wie Van Beneden angiebt, mit dem gem.eiiien Dist. hepatieum identisch." FASCIOLA HEPATICA. 163 similao? organs, one on either side of tlie pharynx, in Amphistoma subclavahim. By the latter authority they are regarded as salivary glands, but Pagenstecher looks upon them as supplementary sucking organs. 164 ENTOZOA. OHAPTBE II. FASCIOLA HEPATIOA. Development of Fasciola hepatica — Eggs and ciliated embryos — Injurious effects of the liver-fluke upon man and animals — Symptoms produced by the Rot — Pathological appearances — Treatment — Summary. Without attempting to enter into such minute details as would extend this work beyond the proper limits, I shall here briefly indicate the extent of our knowledge regarding the developmental process so far as it concerns the earlier stages of the species under consideration ; omitting all hypothetical views concerning the later stages, because it is highly probable that we shall soon be in pos- session of most of the principal facts relating to the phenomena of the intermediate and later stages of development, as they occur in this trematode. Development. — Stated briefly, the formation of the ova takes place in this manner. Yelk globules pass down the various vitel- ligene ducts into the main lateral and transverse efferent canals, until they arrive at the point of union between these passages. ISTear this situation, in an enlargement of the duct specially set apart for the purpose, and where it is joined by a short germigene duct, the globules congregate and surround the individual germinal vesicles coming from the ovary. At this spot, therefore, we have the earliest stage of egg-formation prior to the act of impregnation, which latter function is accomplished by the union of the fine thread- like spermatozoa almost at the same locahty, but a httle lower down. The free seminal elements themselves form extremely delicate threads, of an irregularly spiral form, and measuring the ^7 of an FASCIOLA HEPATICA. 165 incli in their long diameter. Below the point in question the extreme upper end of the oviduct is developed into a special pouch- like organ, known as the posterior semiaal vesicle of Von Siebold. In this receptaculitm semmis the threads lie coiled together en masse, and appear to perform the very act of impregnation as the egg- germs pass downwards into the commencement of the oviduct. Having once arrived at this situation, the first envelope of the egg is developed from a secretion furnished by a special shell-gland, and during the passage of the ovum along the oviduct, into which it has now entered, a second finer shell is formed upon the first. According to Leuckart, the horny chitinous secretion subsequently deposited on the outer sheU-membrane is derived from another special set of chituie-secreting gland-cells, lining the oviducal canal. The same authority adds, " Both the membranes refi-act light highly, but they present a difierent hue. The inner one being green and the outer one of a reddish tint, the usual yellow colour FlO. 36. — Egg oilasciola hepatica in an early stage of yelk-segmentation (X 280 diam.), — Original. of the egg undoubtedly owes its origin to the mixture of these two colours." This also accounts for the marked differences in the degree of colouring observed according to their situation in the con- tinuous oviducal and uterine canal. Pale and almost colourless at first, it is only when they have reached the central uterine passage that they have finally acquired their full, bright, brownish-yellow colouring. At the time of their highest uterine development or period of 166 ENTOZOA. departure from the maternal organs, the eggs display an average longitudinal diameter of iso", whilst their greatest transversal mea- surement is about Wo'. They are, therefore, of no iaconsiderable size, although, as is estimated by Leuckart, the uterus of a fall- grown fluke may contain as many as 45,000 separate ova, at any one given time. When ready for expulsion the contents of the ova display an irregular granular matrix, in which a number of variously- sized oil-like globules are conspicuous, the whole contents being surrounded by a thin yelk-membrane. According to my own obser- vations made on ova placed in water (January 6, 1863), the contents soon afterwards acquire a more definite shape, but did not arrive at an imperfect stage of embryonic development until the expiration of about six weeks (March 16). Leuckart, however, has watched these changes' more fully, and has traced them much farther than myself. He states, as a general proposition, first, that " the eggs of the hver-fluke continue their development outside the maternal body in water, each finally secreting an embryo, which, after the manner of other distomes, swims about freely by the assistance of a imi- formly-developed, ciliated covering."* Distinct peripheral cells having been formed out of the contained granular mass, the embryo first makes its appearance in the form of a more or less oval, cen- trally-placed, well-defined body. As growth proceeds, the peri- pheral cells break down, their place being occupied by the charac- teristic oil-like yelk globules, which assume every degree of size, and by a gradual coalescence ultimately form a transparent mass almost as large as the embryo itself. After a while, the embryonic body elongates and displays traces of segmentation, in which stage it thus exhibits an anterior section capped by a small papillary eminence, a cephalic or second segment supporting a clearly- defined pigment spot, or eye, in the form of a cross, and a third or body segment constituting one half of the entire embryo. Until water had been permitted to gain access to the interior of the shell, * " Die Menschlichen Parasiten," s. 564 FASCIOLA HEPATICA. 167 Leuckart could not clearly recognize the existence of a ciliated covering, but on breaking the shell- walls the ingress of water soon revealed the presence of a long wavy hne surrounding the entire body. In an earUer stage I have myself observed distinct appear- ances of segmentation of the embryo as well as other co-ordinating phenomena precisely similar to those which Leuckart so minutely describes. I was much puzzled, however, with certain appearances which these eggs displayed on being broken up ; for along with the embryo there escaped a number of amoeboid bodies, which moved about actively. On showing my figures of them to Leuckart, he Tig. 37.—; of Fasciola hepatica, containing incxjmpleteljf developed embryos (x 300 diam.).- Original. decided that they were parasitic confervoid zoospores, being, in all respects, similar to those he had himself seen and described as re- ferable to the genus Ghytridium. The structure of the embryo at the time of its escape from the egg-coverings is exceedingly simple. It has the form of a long cone inverted, the anterior extremity being flatly convex or almost truncate, with a central proboscis-like papilla, devoid, apparently, of cilia. The tail is bluntly pointed. The general ciliated cover- ing rests on a well-defined, finely granular epidermis, the latter being succeeded by a thick peripheral layer of large nucleated cells, 168 ENTOZOA, measuring individually m"- The epidermis has a thickness of ^". In the central parenchymatous mass no internal organs are distin- guishable, but Leuckart observed faint indications of a canal toward the hinder part, the caudal extremity sometimes displaying, he thought, evidences of a cleft, as if there were an opening. Fia. 38. — Ciliated free swimming embryo of Fasciola Jiepatica. — Leuckart. As long as the ciliated covering remains intact, the embryo, like other animalcules, displays great activity, whirling round and round on its own axis, and also describing gyrations and circles in the water of different degrees of range, the latter movements being accomplished by bending the body upon itself to a greater or lesser curvature. We have seen Stentor and other infusoria exhibiting the same behaviour, and, as Leuckart observes, with his newly- discovered embryo, when these creatures knock against any obstruc- tion, they pause after the blow, as if to consider the nature of the substance they have touched. In the case of the fluke embryo the ciliated covering eventually falls off, when the embryo re-assumes a more or less oval figure, at the same time changing its swimming mode of progression for the less dignified method of creeping. In the free ciliated condition the embryo of the common liver-fluke measures, according to Leuckart, bc" in length, the anterior broad end being m"- The cilia have a longitudinal measurement of i^". Up to the time at which I write, the subsequent changes which FASCTOLA HEPATICA. 169 the embryo of Fasciola hepatica undergoes are not clearly defined. Moulinie and others have referred to certain of the Oercarise, and the higher forms of trematode larvae as the young of our fluke, but it cannot yet be positively asserted that we know the higher larval conditions of this parasite. Undoubtedly, we may, by inference, form a tolerably accurate notion of the ulterior changes which our embryo undergoes before it arrives at the true distome-type of structure ; but in doing this we can only form our general conclu- sions from data furnished by the history of the development of other well-known species. The course of development usually pur- sued has already been illustrated in the case of Bistoma militare in the early part of this work (pp. 23 — 32), where I have also recorded Pagenstecher's conclusions in regard to the development of trema- tode larvae in general. At this point, therefore, I shall quit the subject of fluke development, only referring to it again when ofier- ing a final brief resume of the principal facts bearing upon the origin, development, and destiny of the species under consi- deration. Injurious Effects upon Man. — Though of comparatively rare occurrence in the human body, the common Hver-flake is, in an indirect manner, extremely injurious to man. By its prevalence in the lower animals it cuts off" a large supply of healthy food, at the same time producing a quantity of meat unfit for the market, but which, nevertheless, is largely eaten by our poorer inhabitants. Even the odour arising from the diseased condition of the animal's flesh is not without its baneftd efiects, and in one instance, at least, it appears to have been the immediate cause of death. In the month of August, 1854, says Mr. Simonds, in his admirable trea- tise on the Rot, " a person of intemperate habits, following the occupation of a country butcher, was employed in skinning and dressing a number of rotten sheep on the premises of a farmer in the county of Norfolk. The sheep were necessarily opened when warm, and while he was so engaged, he complained greatly of the sickening smell. The same evening he was attacked with choleraic 170 ENTOZOA. disease, and two days afterwards was a corpse."* This case is higlily instructive, and when taken in connection with the well- known fact that animals affected with the disease putrify very rapidly, it clearly points to the necessity of removing slaughter- houses far away from densely populated localities. But, as remarked in the outset of this article, the Fasciola hepatica has also been several times known to gain access to the human body. Altogether — excepting the instances mentioned by Ohabert, which I regard as spurious — some fifteen instances have been recorded, but in Leuckart's opinion five only are certain, four others being considered probable. A careful record of these instances is given by Davaine in his elaborate work, along with other cases which must for ever remain doubtful, f The satis- factory instances are those recorded by Duval, Frank, Partridge, Giesker, and Dionis ; the scarcely less probable ones being those noticed by Pallas, Fontassin, Harris, and Fox.| In my opinion, the two last-named cases are entirely satisfactory, and it is, at least, quite certain that the flukes transmitted by these gentle- men to Professors Busk and Owen could be referred to no other species of distome. The cases recorded by Brera and Treutler are doubtful, whilst that of Mehlis is regarded as altogether fictitious. A more probable instance is the one described by Biermer and Lambl, in the "Prager Vierteljahrschrift," for 1849. The cases of Borel, Bidloo, and Malpighi also rest on insufl&cient data. On the whole, however, it is quite evident that this parasite is Hable to invade man, and there cannot be a shadow of doubt that instances have occurred where its presence has been overlooked, and therefore unrecorded. The rarity of its occurrence, however, is sufficiently explained by the circumstance, that man in a civilized condition can seldom have occasion, either * See Simonds, in the Bibliography. t " Traite des Entozoaires," p. 251, et seq. See also Leuckart's work, p. 575. X To these may also be added the case recently recorded by Dr. H. V. Carter in the " Bombay Medical and Physical Society's Transactions," for 1862. — See Bibliography. PASCIOLA HBPATIOA. 171 accidentally or otlierwise, to swallow the intermediate moUus- can hosts in which the higher larv^ of this parasite probably dwell. The circumstance that the fluke has several times been found in abscesses beneath the skin, seems to me to indicate that the animal in its highest larval state possesses a special boring apparatus, snch, for example, as we find in the case of Gercaria ornata. Injurious Effects on Animals. — It is well known that the liver- fluke is extremely destructive, carrying off in England alone some tens and even hundreds of thousands of sheep annually, besides afflicting in a less degree our larger cattle. A writer in the Edin- burgh "Veterinary Review," for 1861, says this "scourge of the ovine race has occasionally reduced the number of sheep so much as to materiaUy enhance the price of healthy animals. For instance, in the season of 1830-31, the estimated deaths of sheep fi?om rot was between 1,000,000 and 2,000,000. By supplying turnip, oleaginous cakes, and grain, sheep partially affected can be fattened ; and those not affected can be kept sound by a limited daily allow- ance of one or other of these foods." Supposing the number to have been 1,500,000, this would represent a sum of something like £4,000,000 sterling ; consequently, as I have before remarked, the disease cannot fail to prove highly prejudicial to our social interests. Every year a large number of sheep perish, but the endemic is much more strongly pronounced in some years than in others. The disease thus produced is variously named in diBFerent countries, and also in different parts of the same country. Thus in England it is now most commonly called, simply, the rot; but in Devonshire, Dorsetshire, and Cornwall, it is called the coathe; whilst in Somersetshire and the western part of England generally, it is known as the bane (Simonds). The terms water-rot and fluhe-rot are of course synonymous. In France the disease is vulgarly termed jpomriture, but the name generally employed, in books, is cachexie aqueuse. In Germany the disorder is called Egelseuche, which, literally rendered, means the 172 ENTOZOA. liver-leecli plague ; in systematic works, however, it is emphatically denominated die Leherkrankheit, or Fdule. As instances of its disastrous effects upon the revenues of agriculturists, we may cite the statements of Davaiae, as suc- cinctly quoted by Leuckart, and also individual cases recorded by Simonds. "In the neighbourhood of Aries alone, during the year 1812, no less than 300,000 sheep perished, and at Nimes and Montpelher 90,000. In the inner departments, during the epidemic of the years 1863-64, many cattle-breeders lost a fourth, a third, and even three-fourths of their flocks." On the same score, our English authority furnishes a variety of painfd cases. Thus, on the estate of Mr. Cramp, of the Isle of Thanet, the rot epidemic of 1824 " swept away £3000 worth of his sheep in less than three months, compelling him to give up his farm." Scores of cases are on record where our Enghsh farmers have individually lost three, four, five, sis, seven, and even eight hundred sheep in a single season ; and many agriculturists have thus become completely ruined. Remarkable periodic outbreaks of this disease are recorded by Simonds as occurring in England in the successive years of 1809, '16, '24, '30, '63, and '60; whilst, for France, Davaine mentions 1809, '12, '16, '17, '20, '29, '30, '53, and '64 as the most remark- able years. It would be interesting to know how far these out- breaks tally with the similar outbreaks which have occurred in Holland, Germany, and other European districts ; for, even here, we perceive that the disease was prevalent during four separate years iu France and England at one and the same time. This, indeed, is no more than we would naturally expect, considering that the extent of the development of the larval forms must,- in a great measure, be dependent upon atmospheric conditions. A warm and moist season would ahke prove beneficial to the develop- ment of the larvaa and their intermediate moUuscan hosts. Their numbers would also multiply enormously ; for, as Pagenstecher has shown, the degree of non-sexual production of trematode larv^ within their sporocysts is materially affected by atmospheric PASCIOLA HEPATICA. 173 changes. On the other hand, a fine, dry, open season, will tend to check the growth and wanderings of the larvee, and thus render the flocks comparatively secure. Considerations like these sufficiently explain many of the crude theories which were early propagated concerning the causes of this disease, and in particular, the very generally prevalent notion that water, and water alone, was the true source of the disease. Intel- ligent cattle-breeders and agriculturists have all along observed that the rot was particularly virulent after long-contiaued wet weather, and more especially so, when there had been a succession of wet seasons. Co-ordinating with these facts, they Ukewise noticed that the flocks grazing in low pastures and marshy districts were much more hable to invasion than those sheep which pastured on higher and drier groimds, but a note- worthy exception occurred in the case of those flocks feeding in the salt-water marshes of our eastern shores. The latter circumstance has suggested the common practice of mixing salt with the food of sheep and cattle, both as a preventive and curative agent ; and there can be little doubt that this remedy has been attended with more or less satisfactory results. The intelligible explanation of the good effected by this mode of treatment we shall find to be intimately associated with a correct understanding of the genetic relations of the entozoon in question, for it is tolerably certain that the larv^ of Fasciola hepatica exist only in the bodies of iresh water snails and small aquatic animalcules. At the present time we are almost in a position to affirm that, ere long, all the main facts relating to the origin and production of the rot-disease will be satisfactorily brought to hght. In the meantime, however, we beg to inform estate owners, agriculturists, sheep-farmers, stock-masters, and all other parties interested in the welfare of flocks and in the production of cheap and wholesome food, that a true solution of this important economic question, in so far as it relates to the production of healthy meat, can only be obtained by the fiirther prosecution of our experimental researches. 174 ENTOZOA-. In this attitude only can we ultimately hope to achieve a certain knowledge of the means of preventing, if not of entirely eradicatingj this fearful disease ; and the writer confesses that it seems to him strange that the cost of these necessary experiments should hitherto, in this country at least, have exclusively rested with those who have given much time, aided by such talents as they may possess, to practically scientific inquiries. On independent grounds he has himself, year by year, sought to throw hght upon the origin and development of the various internal parasites which either annoy or destroy our valuable animals ; and as, in some instances, these experiments have proved eminently instructive, he cannot avoid expressing his thanks to the Association which has aided him in these inquiries.* Those who desire to know what has been doing in other lands towards the elucidation of this important subject should, in par- ticular, consult Davaine and Leuckart's works, already quoted, as well as the Treatise, " De la Reproduction chez les Tr^matodes endo-parasites," par J. J. Moulinie. "Bxtrait du Tome III; des Memoires de I'lnstitut Genevois ;" and also the excellent helmin- thological memoir by Dr. H. A. Pagenstecher, of Heidelberg, entitled " Trematodenlarven und Trematoden," at the close of which the author appends a note referring to the work of Moulinie, finally adding, "We are encouraged again to take up our hitherto fruitless searchings among land-snails, and we hope, with M. Moulinie, that the next steps in this direction will clear up the history of the development of Distoma hepaticum." In this desire I heartily concur. Symptoms produced by the Rot. — ^When the disease has far advanced, it is easy to know a rotten sheep, not only by its very look, but still more convincingly, as I have myself frequently tested, by shghtly pressing the hand over the region of the loins. In this region the diseased animal is particularly weak, and the * See " Eeport of British Association " for 1862. FASCIOLA HEPATIOA. 175 pressure immediately causes tim. to wince, at the same time there is communicated to the hand a jdelding sensation totally imlike the firm resistance which one meets with when running the hand down the spine of a sound sheep. In bad cases there is a visible hollowness of the back, associated with a corresponding pendulous condition of the abdomen, and a general emaciation of the body. The spine sticks out prominently, the gait of the animal is feeble, its whole appearance being dull, dejected, and melancholy in the extreme. " The general surface of the skin," says Professor Simonds, " loses its ruddy hue, and becomes deficient of the unctuous secretion which in health belongs to it. This renders the wool harsh and dry, and leads also to its easy separation from the follicles. A dry, scaly state of the skui on the inner parts of the thighs, particularly where it is uncovered with either wool or hair, is likewise early ■fco be recognized." In less advanced cases, the same authority observes, "an examination of the eye will materially assist in determining the question of disease. If the lids are everted, the membrana nictitans being pressed forward, it will be found that in the early stages of the malady — and especially if the animal has been excited by being driven a short distance— the vessels of the conjunctiva are turgid with pale or yellowish- coloured blood, and that the whole part has a peculiar moist or watery appearance. Later on, the same vessels are blanched and scarcely to be recognized, excepting, perhaps, one or two, which present a similar watery condition, or are turgid with dark-coloured blood." Some other symptoms might be mentioned, but the above are sufficiently numerous and thoroughly charac- teristic. Pathological Appearances. — On cutting up a thoroughly rotten sheep the appearances which present themselves to the scientific pathologist are perhaps fully as striking as they are to the butcher himself. One instantly notices the wasted, flabby, watery condi- tion of all the tissues, and a total absence of that fresh, firm, car- neous look which so distinctively characterizes the flesh in a state 176 ENTOZOA. of tealtli. Not only is the rigidity and firm consistency of the muscles altogether wanting, but these structures have lost that deep reddish colour which normally exists. When the abdominal cavity is opened a more or less abundant, clear, limpid, or yellowish fluid win make its escape, and the entire visceral contents will, at the same time, display a remarkably blanched aspect. These pathological changes are also shared by the important organ espe- cially affected, namely, the Hver. This gland has lost its general plumpness, smoothness, and rich, reddish-brown colour, and has become irregularly knotted and uneven both at the surface and the margins ; its colouring being either a dirty chocolate brown, more or less strongly pronounced at different parts, or it has a peculiar yellowish tint, which ia places is very pale and conspicuous. To the feel it is hard and brawny, and when incised by the scalpel, yields a tough and, in places, a very gritty sensation. On opening the gaU-ducts a dark, thick, grumous, bihary secretion oozes slowly out, together with several distomes, which, if not dead, slowly curve upon themselves, and roU up like a sHp of heated parchment. On further shtting open the biliary passages, they are found distended irregularly at various points, and in certain, situations many flukes are massed together, having caused the ducts to form large sacs, in which the parasites are snugly ensconced. The walls of the ducts are also much thickened in places, and hardened by a deposit of coarse calcareous grains on their inner surface. Mr. Simonds says, that " the coats of the ductus hepaticus, as also of the ductus com/m/w- nis clioledicus, are not unfrequently so thick as to be upwards often times their normal substance, and, likewise, as hard as to approach the nature of cartilage." Respecting their numbers, the greatest variation exists. The presence of a few flukes in the Hver is totally insufficient to cause death ; consequently, when a sheep dies from rot, or is killed at a time when the disease has seriously impover- ished the animal, then we are sure to find the organ occupied by many dozen, many score, or even several hundred flukes. Thus from a single hver Bidloo obtained 800, Leuwenhoeck about 900, FASCIOLA HEPATICA. 177 and Dupuy upwards of 1000 specimens. Even the occurrence of large numbers only destroys the animal by slow degrees, and, pos- sibly, without producing much physical suffering, excepting, per- haps, in the later stages. Associated with the above-described appearances, one also not unfrequently finds a few flukes in the intestinal canal, whilst a stiQ more interesting pathological feature is seen in the fact that the bUe contained in the hver ducts is loaded with flukes' eggs. In some cases there cannot be less than tens or even hundreds of thousands. Not a few may also be found in the intestinal canal, and in the excreta about to be voided. Occasionally dead specimens become surrounded by inspissated bile, and gritty particles deposited in the hver ducts ; thus forming the nuclei of gaE stones. Mr. Simonds mentions a remarkable instance, " where the concretion was as large as an ordinary hen's egg, and when broken up was found to contain about a dozen dead flukes. It was lying in a pouch-hke cavity of one of the bihary ducts."* Lastly, it need scarcely be added that it is by no means unfrequent to find one or even several other kinds of entozoa co-existing with the Fasciola in the same sheep, the most common form being that of the larval EcMnococcus. Treatment. — No one doubts that "prevention is better than cure," and as in the present state of our knowledge we are in a position to offer many suggestions, which, if properly carried out, cannot fail to be of service in checking the fluke malady, it is, in the first instance, desirable to make a few remarks on this head. Moisture being essential to the growth and development of the fluke-larvas, it is clear that sheep cannot be infected so long as they remain on high and dry grounds, and even in low pastures they can scarcely take the disease so long as they are folded, and fed on hay, turnips, and fodder procured from drier situations. At * In this place one naturally calls to mind, the statements of Mr. Garner, who asserts that he has found solitary examples of dead distomata forming the nuclei of pearls, in our common river mussel ; a Continental observer has noticed the same thing. See " Reports of the Cambridge Meeting of the British Association for 1862." A A 178 ENTOZOA. farmers' meetings I have endeavoured to enforce the expediency of these plans, but, as Mr. Simonds himself has very truly observed, every man depends rather upon his own " preconceived notions of ■ the disease than on any precise scientific information of its natiire ;" and so it happens that one resumes one's seat with the feeling that, so far as entozoological science is concerned, men appreciate " darkness j rather than light." This language may appear harsh, but it is, nevertheless, true. To a certain extent, and partly fi?om other considerations, it must be admitted that some few enlightened agriculturists have adopted those very plans which science pronounces to be correct, and they have, in the end, been amply rewarded for their judicious discernment. As regards the human body, it is obvious that we can only be- come infested by flukes in one or other of two ways. In then- highest larval condition, the parasites either penetrate the sMn directly from without, or they are carried into the stomach along with our food, out of which latter viscus they grope their way into the liver. It is highly probable that both these methods of inva- sion are adopted. In the first case, it is clear that the free larvae will have been obtained from water used to bathe the person, or from the naked skin being exposed to the surface of moist grass or herbage wherein the larvse or their moUuscan hosts abound. In the second case, they will have been obtained by the iadividual's having partaken of watercresses, or other field- herbs, in afresh or unwashen state. Even celery and other market-garden vegetables may har- bour the fluke-larvae, especially in cases where such gardens have been watered by the contents of weedy ponds and stagnant ditches. As other parasites may be conveyed to us in the same way, it behoves all parties concerned in the sale and preparation of vegetable food to subject such matters, in every case, to a thorough douche with clean pump or reservoir water. Only after this simple cleansing can the aforesaid vegetable products be declared free fi^om trema- tode and other helminthic larv«. It is a noteworthy circumstance that most, if not all, of the cases of Fasciola hepatica infesting the PASOIOLA HEPATICA. 179 human body have occurred in individuals of the lower classes, who would naturally be careless as to the thorough cleansing of water- cresses and other vegetables procured from the garden or the field. In respect of the method of treatment to be adopted where the parasite has gained access to our bodies, little, of course, need be said. This animal's presence, indeed, could only be diagnosed by the accidentally observed fact that flukes or their ova had been voided ; and even then, the exhibition of a purgative would do no more than reheve the intestine of the few specimens which might happen to be lodged in it. Those in the liver would remain un- touched; and even mercurial remedies would be of httle avail, except in so far as they might increase the flow of healthy bile, and tend to clear the gall passages. Those found in cavities beneath the skin could never be diagnosed, and if they could, would serve no other uidications for surgical interference than are supplied by ordinary abscesses themselves. In like manner, when the malady has become fairly developed in the sheep, iaternal remedies are of httle avail, at least, in view of producing a thorough cure. Palhative treatment may un- doubtedly do good, especially in cases where the disease is not very strongly pronounced. The most important thing is the transfer- ence of the rot-affected animals to dry ground and good shelter ; supplying them, at the same time, with a hberal quantity of manger food, such as beans, peas, and other leguminous seeds. The fodder, of whatever kind, should be fi^equently changed, and many other hygienic measures adopted, all tending to promote the appetite and general health of the animal. An admixture of salines is a matter of essential importance, especially in cases where the disease is not far advanced. The beneficial effect of salt is one of those few points on which nearly all parties are agreed, and its preservative influence in the case of sheep fed upon salt-water marshland has been previously explained. In regard, however, to the legion of remedies which have from time to time been proposed, all I need 180 ENTOZOA. here say is, that most of them when fairly tested have been found to fail ignominiously. Every year we hear of the adoption, often with enthusiasm, of new so-called specifics, or of ancient medicines whose employment had long fallen into disuse. Thus, for ex- ample, in the April number of the " Journal des Veteriaaires du Midi," for 1860, we find M. Raynaud strongly recommending soot, in doses of from one to three spoonfuls, to be followed up by the administration of a grain of lupin for tonic purposes. In like man- ner, we have received from France wonderful accounts of the me- dicinal virtues of a certain foetid oleaginous compound, the value of which has been lately put to a fair test by our distinguished vete- rinarian, Professor Simonds. This last-named gentleman having with infinite care and trouble undertaken a series of experiments with the nauseating remedy in question, informs us, ia the " Scot- tish Farmer and Horticulturist," as a result of his inquiries, that he fears " we must conclude that this supposed cure of rot in sheep has proved quite ineffective for good in our experience." Finally, in regard to the merits of Mr. Youatt's method of treating the malady, as if it were an ordinary inflammation of the hver, reqiiir- ing the adoption of bleeding and other sharp, antiphlogistic mea- sures, one can only regard the plan as altogether a mistake. However, those who desire further knowledge on this point should consult the admirable essay by Mr. Simonds, to which I have so frequently had occasion to allude. Summary. — Correlating all the known data afibrded by the ex- perience of our best veterinary authorities, by observant naturalists generally, by my own researches, and by the recent experimental investigations of Continental helminthologists, I may here state in a tentative manner the conclusions to which a due consideration of all these facts inevitably lead. The deductions here recorded may eventually require modification in respect of their minor details ; but in the main they will be found substantially correct, and there- fore be likely to convey that kind of information which can scarcely fail to interest those more immediately concerned in the preserva- FASOIOLA HEPATICA. ]81 tion of cattle, as well as those also who regard the subject from a wider social point of view. It is even now encouraging to think that when a little more hght shall have unveiled all the missing links now wanting to complete the chain of evidence, the promo- ters of science will more hopefully seek to enlighten those who, in so far as natural history knowledge is concerned, are unwisely cling- ing to the idle " tales of a grandfather." Surely an enlightened pubhc will no longer esteem the vague opinions of a bygone age to be more worthy of credit than the clearly enunciated facts of recent scientific discovery, 1. The Fasciola. hepatica, or sexually-mature hver- fluke, is especially prevalent in sheep during the spring of the year, at which time it constantly escapes from the ahmentary canal of the host, and is thus transferred to open pasture-grounds. 2. It has been shown by dissections that the hver of a single sheep may, at any given time, harbour several hundred specimens of the fluke, and it is certain that every mature entozoon wiU con- tain many thousands of minute eggs. 3. The escaped flukes do not exhibit powers of locomotion sufficient to prove them capable of undertaking an extended migra- tion, but their movements may subserve the purpose of concealing them within the grass or soft soil where they have fallen. Their habit of coiling upon themselves probably facihtates the expulsion of their eggs. 4. The eggs can only escape from the oviduct of the entozoon one at a time, but there is no doubt whatever that prodigiously large numbers of loose ova are expelled the infested sheep in the same manner as the flukes themselves. 5. By the dispersing agency of winds, rains, insects, feet of cattle, dogs, rabbits, and other animals, and even by man himself, the eggs are carried in various directions, not a few of them ulti- mately finding their way into pools, ponds, ditches, canals, and running streams. 6. The freed eggs, at the time of their matmnty, contain ciliated 182 ENTOZOA. embryos, capable of active progression wlien brought in contact with dew on the blades of grass, rain-drops, pools of water, ponds, and lakes. The prolonged action of moisture without, aided by vigorous movements of the perfected embryo within, serves to loosen the lid-hke end of the egg-shell, by the opening of which the animalcule is set free. 7. The cihated embryo, which is furnished with a solitary X-shaped eye, after a longer or shorter period of activity, loses its cihated covering, and becomes comparatively inert. It alters its form, and probably soon afterwards gains access to the body of a fresh-water mollusc, or, possibly, into the tissues of a land-snail. 8. Once within the viscera or substance of its so-called interme- diate host, the Uon-ciliated larva probably becomes transformed into a large sac, and developes new larvae within its interior. These sac-hke larvae are called " nurses/' or " sporocysts," or, when rather highly organized, "rediae." 9. The contained nurse progeny or higher trematode larv^ are probably furnished with tails, as in other flukes. When fully de- veloped, they constitute the well-known Oercari^. 10. The Cercari^ have a tendency to migrate from the bodies of their molluscan hosts, and they are quite capable of an independent existence. During these wanderings in the water, they are occa- sionally brought in contact with the human body, and in a few instances appear to have succeeded in penetrating the skin. 11. It is not certain whether the Cercarise are taken into the bodies of quadrupeds when the latter are drinking water or eating sohd food, but it is probable that they are passively transferred in either way. It is not unhkely that they are often swallowed while still resident with the bodies of their molluscan hosts. 12. From the digestive organs of sheep or cattle the Cercarise make their way into the liver, in which new situation they proba- bly part with their tails, and become encysted. This constitutes the so-GaUed pupa stage. FASOIOLA HEPATICA. 183 13. The pupa, thus encysted for many weeks, or even months, attains a higher organization, at last becoming converted into the sexually mature Fasciola hepatica. It gains access to the Hver ducts, then passes into the common biliary outlet, and from thence is transferred into the intestinal canal, being finally expelled its vertebrate host in the manner previously described. 184 ENTOZOA. CHAPTER III. DISTOMA LANCBOLATUM. Flukes with a simple unbranclied intestine — Distoma lanceolatum — General and specific characters — Its non-identity -vrith. Fasciola hepatica — Kichner's interesting case — Lenckart's account of the embryo — Distoma opJithalmohium — D. crassum and D. heterophyes — Bilharzia hcsmatobia — General and specific characters — Structure and development — Injurious efiects on man — Tetrastoma renale — Hexathyridium pinguicola and S. venarum. So far as is at present known, there are but two species of flukes which display a dendroid or branched digestive apparatus. These have both been described in the foregoing chapters, and, therefore, I now pass to the consideration of those trematodes which have a simple, bifurcated intestine, or, in other words, those species of human parasites legitimately allocated under the generic title of Distoma. They are, in short, the distomes properly so called ; but as, in the non- systematic part of this work, it is unnecessary to insist on such rigidly- scientific definitions, we shall here continue to speak of the trematodes as distomes or flukes, indifferently, whether we refer to members of the genus Distoma, or to those of the allied genera Fasciola, Gampula, Bilharzia, and Hexathyridium. Those persons who are only acquainted with the human entozoa may be reminded that the family of flukes (Distomidce) embraces a great many other genera than those above indicated, all of which will be found named, and some described, in the systematic part of this treatise. 2. Distoma lanceolatum. D. lanceolatum, MeHis ; Bucholz ; Dujardin; etc. D. hepaticum, Zeder ; Rudolphi ; Bremser ; etc. DISTOMA LANCEOLATUM. 185 Bicroccelmm lanceolatum, Dujardin ; Weinland. Fascioln hepatica. Block ; Jordens ; Bosc. F. lanceolata, Rudolplii ; Moquin-Tandon. Plmmria latiiiscvla, Goeze. General and Specific Characters.— A small, flat trematode helminth, measuring rather more than the third of an inch in length, and about one line and a-half in breadth, being also especially characterized by its lanceolate form ; the widest part of the body corresponds with an imaginary hue drawn opposite the spot where the blind intestinal tubes terminate, and from this point, on either side, the width of the animal becomes gradually narrowed towards the extremities ; both ends are pointed, but the inferior or caudal one more obtusely than the anterior or oral end ; the general surface is smooth throughout, and unarmed; the reproductive orifices are placed in the central line imme- diately in front of the ventral sucker, and below the point at which the intestine bifur- cates ; the oral sucker is nearly terminal, and jo" in breadth, the ventral acetabulum being about the same diameter ; the testes form two lobed organs placed one in front of the other in the middle line of the body and directly below the ventral sucker ; the uterine canal is remarkably long, forming a series of tolerably regular folds, which occupy the central and hinder parts of the body, reaching almost to the caudal extremity. The vitelligene glands cover a limited space, on either side, near the lateral borders of the animal, the foramen caudate communicates with a contractile vesicle, which passes up- wards in the form of a central trunk vessel, early dividing into two main branches ; these latter reach as far forwards as the oesophageal bulb, opposite which organ they suddenly curve upon themselves, retracing their course for a considerable distance backwards ; the digestive canals are sUghtly widened towards their lower ends, which occupy a line nearly corresponding with the commencement of the lower fourth of the body ; the ova are conspic:ious within the uterine folds, and gradually pass from a dark -brownish colour in front to a pale-yellow colour behind. This species, though., comparatively speaking, little known, is by no means of rare occurrence in the sheep and ox. Dujardin constantly met with it in the former of these two ruminants, and he also, in common with Goeze and Bremser, detected it in the pig. Rudolphi observed it in the red deer {Gervus elaphus), and Schaffer in the fallow deer (Gervus dama). It has also been noticed in the rabbit and hare by Zeder and Bremser, and even in the cat (by Eudolphi and Siebold) according to Dujardin ; but, probably, the most common place of abode of this fluke, in the adult con- dition, is the liver of the ox. Mehhs was the first to establish the non-identity of this species with the common fluke; a view, which was also shared by Schaffer and Rudolphi, but subsequently abandoned by the latter. B B 186 ENTOZOA. Only three instances of the occurrence of this well-marked form in the human subject are, at present, on record. The first is that of Bucholz, who found a considerable number of these little flukes m the gall-bladder of a prisoner who died from fever at Weimar. The specimens, which are stiU preserved in the Museum of the Univer- sity of Jena, have been re-examined by Leuckart, who pronounces Fig. 39. — FuU-grown Distoma lanceolatmn, showing the reproductiye and digestive apparatus ; highly magnified.— Blanchard. them to be certainly referable to B. lanceolatum. The second is the case of Ohabert, which occurred iu France. In this instance a large number of specimens were expelled the intestines of a girl twelve years of age by the administration of empyreumatic oil. The third example is one of comparatively recent date, for the particu- DISTOMA LANCEOLATUM. 187 lars of which we are indebted to that indefatigable helmintho- logist Eudolf Leuckart, to whom the case was communicated by Dr. Kichner, of Kaplitz in Bohemia. As this case is highly interest- ing and instructive, I give an abstract of it, as follows :* — " Dr. Kichner's patient was a young girl, the daughter of the parish shepherd at Kaplitz, having been accustomed to look after the sheep ever since she was nine years old. The pasture where the animals fed was enclosed by woods, being traversed by two water-dykes, and being, moreover, also suppHed by ten Httle stag- nant pools. These reservoirs harboured numerous amphibia and molluscs (such as Lymnceus and Paludina), and the child often quenched her thirst from the half-putrid water. Probably she also partook of the watercresses growing in the ditches. At length her abdomen became much distended, the limbs emaciated, and her strength declined. Half a year before death she was confined to her bed, being all the while shamefully maltreated by her step- mother. Dr. Kichner only saw her three days before her death, and ascertained that she had complained of pain (for several years) over the region of the liver. A sectio cadaveris was ordered by the Grovemment, when (in addition to the external evidences of the cruel violence to which the poor creature had been subjected) it was found that she had an enormously enlarged Hver, weighing eleven pounds. The gall-bladder, which was very much contracted and nearly empty, contained eight calculi and forty- seven specimens of the Distoma lanceolatvm,, aU of which were sexually mature." Considering the facts of this singular case, one can have no dif&cidty in arriving at the conclusion that these parasites were obtained from the girl's swallowing trematode larvse, either in their free or in their encysted condition. Leuckart says it was not possible to ascertain whether the parasites had any connection with the gall-stones, or whether the two maladies, so to speak, were in- dependent of each other ; yet this question might possibly have * " Die MenscMichen Parasiten." Erst. Bd., s. 608, et seq. 188 ENTOZOA. been solved if the calculi had been broken up, in order to ascertain their structure. It is just possible that dead distomes may have formed their nuclei, and if so, the circumstance would, of course, point to the worms as the original source of the malady. Into the minute anatomy of this trematode it is unnecessary to enter at any length, because, in the main, its structure corresponds with that of Fasciola, although great differences obtain in respect of the form and disposition of the internal organs. These have been partly indicated already, but there are still some points worthy of consideration. Thus, in connection with the digestive system, Walter has described a special set of salivary organs. Leuckart, who appears to attribute to them an independent fiinction, says that they are readily visible in the living animal. " They are found in rather considerable numbers, scattered over the front part of the body, and appear in the form of large granular cells (measuring g^'), enclosing a globular nucleus, and each of them terminating in a thin and long filiform excretory duct. All the ducts are directed forwards towards the oral sucker, into which, according to "Walter's description, they open in a partly isolated, and partly combined manner." In other particulars the digestive apparatus is simple, the mouth and muscular pharynx being fol- lowed by a narrow oesophagus, which divides into two blind intes- tinal tubes, which become very gradually widened as they approach their inferior limits. As regards the nervous system, the only distinction worth noticing consists in the more backward position of the commisural filament, which connects the two cephaUc ganglia ; and even here, according to Leuckart, considerable variation occurs. The excre- tory system is well developed, and terminates inferiorly in a very conspicuous sac, which latter is usually filled with active molecular particles, and appears to be capable of extrusion. The repro- ductive organs are, for the most part, easily made' out ; but except as regards the lobulated and simple form of the testes, the greater number and altered position of the uterine folds, and the very DISTOMA LANCEOLATUM. 189 limited extent of the development of the vitelhgene glands, there is little which need be added to the general and specific characters previously described. The development of Distoma lanceolatum is, however, a matter of greater importance, especially since our knowledge of its life- changes suggests an interesting comparison between the earher embryonic stages displayed by the larvse of difierent trematode species. It is to Leuckart that we are indebted for most of the facts bearing upon this subject. In the first place, it is especially worthy of notice that the contents of the ova attain a tolerably high degree of embryonic formation before the eggs quit the uterine or oviducal canal of the parent ; consequently, it is not improbable that the subsequent larval metamorphoses are accomplished with more rapidity than obtains in the case of Fasciola. It would seem, however, that the embryos do not make their escape from the egg- coverings immediately after the eggs have been deposited by the parent, but, according to the experiences of Leuckart, an interval of a few weeks must elapse. In the early condition, the rudimen- tary embryo occupies the centre of the egg, and always has its cone-shaped, cephalic end directed towards the upper pole of the shell, or, in other words, to that end which is furnished with the Ud-hke operculum. In the mature state, whilst stfil within the uterus, the cone-shaped head is supplied with a ciliated crown. Speaking of its intimate structure, Leuckart says, " It is finely granular, and armed at the tip with a dagger-hke spine, which, with the simul- taneous displacement of the adjacent granular mass, can be pushed forward and drawn back again." Besides this so-called cephalic granular mass, there are within the embryonic body two other granu- lar masses widely separated fi'om each other, but occupying the posterior half of the embryo. These Leuckart supposes to be the rudiments of a fixture brood to be developed at the time when the fi:-ee embryo shall have lost its ciliated swimming apparatus, shall have bored its way by means of the cephahc spine into the tissues of a mollusc, and shall have become metamorphosed into a sac-like 190 ENTOZOA. larva (Nurse, Sporocyst, or Redia, as the case may be). What- ever be tlie full significance of these internal developments, we have at least satisfactory evidence that the complete and fi-ee embryo is a globe-shaped animalcule, having the anterior third or cephalic end Fig. 40. — Free embryo of Distoma lanceolaticm j highly magnified. — Leuekart. of the body covered with cilia, and armed with a central boring spine. In consequence of this limitation of the ciliated covering, its swimming movements are less vivacious than those of the embryo of Faseiola hepatica ; it will, therefore, probably take up its residence in a less active host than that chosen by the embryo of Faseiola, selecting one of those molluscs which either move slowly or are prone to keep at the bottom of the water. The mature eggs have a length of els to 6^5 of an inch, and a breadth of ^'. The long diameter of the free embryo varies from ^ ' to ^ , the transverse diameter being j^". Whilst the embryos were still in the Qgg Leuekart could see no ciliary motion ; with most observers, both the ciliary apparatus and the boring spine appear at this stage to have altogether escaped observation. The further transformations of the embryo and larvse of Distoma lanceolakom are not known with certainty, but our conjec- tures on tliis score cannot be far removed from the actual truth. We shall probably find that the embryo changes into a Sporocyst, the latter producing, directly or indirectly, a colony of armed cer- carian larvge provided with tails. These higher larval forms may again inhabit moUuscs, after a longer or shorter period of active wandering, being subsequently transferred along with their hosts into the intestinal canal of herbivora, and, in a few cases (probably along with watercresses) into the human stomach. Leuekart DISTOMA OPHTHALMOBIUM. 191 thinks lie lias hit upon the juvenile form of Distoma lanceolatum in the body of Planoriis marginatus, but his feeding experiment to prove this relationship was not thoroughly satisfactory. Future investiga- tion wiU doubtless reveal all the actual stages through which this and many allied fluke- species pass during their progress upwards from the lowest larval to the highest sexually-mature condition. 3. Distoma ophthalmobium. D. ophthalmobium, Diesing; Kuchenmeister ; etc. D. Qentis), Von Ammon. D. oculi-humani, Gescheidt. Dicroccelium oculi-humani, "Weinland. ? Monostoma lentis, Nordmann ; Grescheidt ; Diesing ; etc. ? Festucaria lentis, Moquin-Tandon. I here combine the two so-called species of human eye trematodes under one title, without, however, for a moment sup- posing that we have either in the Distoma ophthalmobium of Diesing or the Monostoma lentis of Nordmann, a genuine sexually-mature fluke. I think it highly probable that both forms may be the young of one distome ; and (as suggested by Leuckart's compari- sons in the case of Distoma ophthalmobium) it is quite possible they may both of them be referable to the species last described {D. Fio. 41. — The BO-called Distoma ophthalmobium ; considerably magnified. — Von Ammon. lanceolatum). Certainly one has a difficulty in believing that so- accurate an observer as Nordmann could have overlooked a ventral sucker, if one were really present ; and yet, on the other hand, the remarkable minuteness of the worm may have served to obscure 192 ENTOZOA. this organ. Similar mistakes have occurred before, as Dujardin and others have pointed out. In the case of the Distoma ophthalmobium Gescheidt found four specimens in the eye of a child five months old, born with lenticular cataract. No one of the examples exceeded half a line in length. They were situated between the lens and its capsule, in which place they could be recognized as so many dark spots on the surface of the lens. From the original description in Von Ammon's " Zeit- schrift fiir Ophthalmologie" we are scarcely warranted in conclud- ing that the specimens were sexually mature. The author speaks of ovaries, bub they were "indistinct," and they are not repre- sented in the carefuUy executed figures given in Von Ammon's writings.* One can scarcely escape the conviction, moreover, that Von Nordmann's Monostoma lentis is identical with this worm; and I perceive that Dr. Weinland, of Frankfort, entertains a simi- lar suspicion. Kuchenmeister's idea that this Monostoma may be a young Gysticercus cellulosce is not at all convincing ; for no one ever heard of eight Gysticerci occupying one eye-baU, and much less is it likely that they should occur thus gregariously in the human lens. Trematodes are seldom sohtary ; and aU the circum- stances render it probable that the worms extracted by Pro- fessor JiiQgken, in his case of cataract, were identical with those removed after death fi'om the eye of the httle girl who died from infantile atrophy whilst under Von Ammon's care. As just hinted, there were eight specimens in this case, the worms having an average longitudinal measurement of about 55 of an inch. Finally, into speculative questions as to how these parasites came into the eye, one does not care to enter, especially as it would lead us at too great length into the consideration of similar phenomena observable in the lower animals. 4. Distoma crassum. D. crasswn. Busk ; Cobbold ; Leuckart ; etc. * " Klinisohe Darstelltingen der Kranklieiteii des menscUichen Auges," vol. i. 1. 12, and vol. jii. 1. 14. DISTOMA ORASSUM. 193 D. Busldi, Lankester. Dicrocoelium Busldi, Weinland. General and Specific Characters. — A trematode helminth varying from an inch and a half to thi-ee inches in length, and having an average breadth of | of an inch; especially also characterized by its uniform and considerable thickness, combined with the presence of a" double alimentary canal which is not branched;" the body is pointed in front, and obtusely rounded posteriorly ; the integument being smooth and unarmed ; the reproductive orifices placed immediately above the ventral sucker : the testes form two bulky, lobed organs, situated below the ventral acetabulum, and disposed in the middle line, one in front of the other ; the uterine folds occupy only the front part of the body, the margins of which also display two viteUigene glands, one on either side of the intestinal' tube ; the excretory organ consists of a central trunk with diverging branches. This is a good species, and appropriately named ; for, althougli Yon Siebold (in Miiller's " ArcHv" for 1836, p. 234, and in his " Lehrbuch," vol. i. p. 143) refers to a Distome infesting Hirundo urhica under this title, he has given no description of the worm. Diesing places Von Siebold' s 2). crassum among his species inqui- I'lG. 42.— Outline drawing oi Distoma crassnm. Busk ; the parts not actually visible, in the speci- mens examined, being indicated by dotted lines; «, oral sucker; J, acetabulum ; o, reproduc- tive papilla ; d, uterine canal ; e, ovary ; /,/, testes ; g, g, g, g, intestinal tubes ; h, aquiferous or excretory canal. — Original. rendfp,, and it is very probably identical with the D. maculosum of Rudolphi. No other instance has occurred since the original fourteen c 194 ENTOZOA. specimens were discovered by Mr. Busk in the duodenum of a Lascar. From a careful examination of three examples, severally presented by the discoverer to the Museum of the Eoyal College of Surgeons, the Museum of the Middlesex Hospital Medical College, and to my private collection,* I am satisfied that it is generically dis- tinct from the above ; but it is unnecessary to insist further on this distinction, as I have already, in this work, exposed the fallacy of combining the genera Fasciola and Distoma. In two of the specimens which Mr. Busk injected with mercury, the injection has passed from the digestive into the aquiferous system, which latter, in its arrangements, does not differ materially fi?om that of Fasciola hepatica. The original account in Dr. Budd's work on diseases of the liver speaks of a "branched uterine tube." This description, however, is manifestly erroneous, and probably refers to the division of the narrow end of the ovarian tube, where it is joined by the two main ducts which come from the yelk-forming glands on either side of the body. 6. DiSTOMA HETEEOPHYES. D. heterophyes, Von Siebold and Bilharz ; Kuchenmeister. Fasciola heterophyes, Moquin-Tandon. Dicrocoelium heterophyes, Weinland. General and Specific Characters. — A minute trematode helmmth, measuring only three-fourths of a line iu length, and one-fourth of a line in breadth ; having an oblong pyriform outline, attenuated in front, and obtusely rounded behind ; body compressed throughout, the surface being armed with numerous minute spines, 'which are particu- larly conspicuous (under the microscope) towards the head ; oral and ventral suckers largely developed, the latter being near the centre of the body, and about twice as large as the former ; pharyngeal bulb distinct and separate from the oral sucker, and continued into a long oesophagus, which divides immediately above the ventral aceta- bulum ; intestinal tubes simple, gradually widening below and terminating near the posterior margius ; reproductive orifices inconspicuous but evidently placed below and a httle to the right of the ventral sucker, at which point they are surrounded by a special accessory organ, resembling a supernumerary sucker ; uterine folds numerous and central, communicating with small but conspicuously developed viteUigene glands ; testes spherical and placed on the same level in the lower part of the body ; ovary distinct ; aquiferous system terminating inferiorly in a large oval contractile vesicle, the latter opening externally by a central /oj-amera caudale. * This specimen is figured in Leuckart's recent work. Erst. Bd., s. 686. D[STOMA HETEROPHYBS. 196 In the month of April, 1851, Dr. Bilharz, of Cairo, discovered this minute parasite in the small intestine of a boy ; and on a second occasion he collected several hundred specimens under very similar circumstances. The parts infested displayed a multitude of reddish points, due to the presence of the dark-coloured ova seen in the interior of the worms. Until recently I had not had an opportunity of examining this trematode, and I am, therefore, much indebted to the friendliness of Leuckart for the couple of specimens which he has had the goodness to send me. The close inspection of these has enabled me to follow out his own accurate and extended descriptions, as well as those supplied by antecedent Pig. 43. — Distoma Tieteropliyes, Von Siebold ; drawn from a specimen suppiied by Leuckart (x 60 diam.). — Original. observers. Without, however, recapitulating the distinctive peculiarities indicated in my account of the general charac- teristics of the worm, it is necessary to draw attention to the very remarkable apparatus surrounding the reproductive orifices. It consists of an irregularly circular disk, measuring ^ of an inch in diameter, and having a thick hpped margin, which supports seventy fish-basket-like horny ribs comparable to the claw- formations seen in the genus Octobothrium. According to Bilharz these ribs give off five little branches from their sides, but Leuc- kart could not see them in his specimens. The latter finds the 196 ENTOZOA. lengtli of these horny filaments to be i^", whilst their breadth is 3570". On the whole we may regard this organ as a complicated form of " holdfast " designed to faciHtate or giye efficiency to the sexual act. I may here also state that this structure is by no means unique, for, if I mistake not, it exists in an equally developed degree in the young trematode which Dr. Leared found infesting the heart of a turtle. Leared believed that he had found a true distome, an opinion to which I could not give my assent, seeing that the organ described by him as a " folded, ventral sucker," presented a very different aspect to the genuine oral sucker displayed by the same animal. I am now persuaded that the structure in question, which is, to a certain extent, characteristic of his so-called Distoma constrictum, is analogous to the supplementary "holdfast" existing in Distoma heterophyes. The opinion also which I then advanced as to the probable source and condition of the parasite, I still see no reason to retract.* In regard to the anatomy of D. heterophyes, I have only further to observe that a special set of glandular organs is situated on either side of the elongated oesophagus, but the con- nection between these striictures and the digestive apparatus is not clearly made out. Leuckart compares them to the so-called salivary glands found in Distoma lanceolatum, and says, " The presence of such a glandular apparatus is also indicated by the more ventral position of the oral sucker, and the development of the cephaKc margin." The conspicuous contractile vesicle terminatiag the excretory system is developed to an unusually large extent, exhibiting in its interior multitudes of the well-known active molecular particles. The ova present a rich reddish-brown colour, having a rather broadly oval figure, and measuring ^^ of an inch in length, by j^" transversely. * Dr. Leared's brief description of this parasite is given in the lOth vol. of the " Quarterly Journal of Microscopic Science," p. 169, and is accompanied by an accurate woodcut. New Series, Vol. II. for 1862. He also found in the blood a quantity of ova precisely like those which Mr. Canton had previously described as adhering to the conjunctivse of turtles' eyes. See a paper in the same Journal for 1861, Vol. I. N. S., p. 40. BILHARZIA HiEMATOBIA. 197 6. BiLHAEZIA H^MATOBIA. B. hcematohia, Cobbold. B. magna, Cobbold. Gyncecophorus hcematobius, Diesing. Thecosoma hoematohmm, Moquin-Tandon. Distoma hcematobium, Bilharz ; Kuchenmeister ; Moulinie ; etc. Bistoma capense, J. Harley. Schistosoma hcematobium, Weinland. General and Specific Characters. — A trematode helmintli in whicli the male and female reproductive organs occur in separate individuals ; the male being a cylindrical vermiform worm, measuring only half an inch or rather more in length, whilst the female is filiform, longer, and much narrower than the male, being about four-fi.fths of an inch from head to tail ; in both, the oral and ventral suckers are placed near each other at the front of the body ; in the male the suckers measuring ~^", in the female ■^" in diameter ; in either, the reproductive orifice occurs immediately below the ventral acetabulum. The comparatively short, thick, and flattened body of the male is tubercu- lated and furnished with a gyncecophoric canal, extending from a point a little below the ventral sucker to the extremity of the tail ; this slit-like cavity being formed by the narrowing and bending inwards of the lateral borders of the animal, the right.side being more or less comipletely overlapped by the left margin of the body ; caudal extremity pointed ; intestine in the form of two simple blind canals. Female with a cylindrical body measuring only ^5 of an inch in thickness in front of the oral sucker ; lodged in the gynaBcophoric canal of the male during the copulatory act ; thickness of the body below the ventral acetabulum being about sW \ ^'^^ ^^ the lower part^V'; surface almost smooth throughout ; intestinal canals reunited after a short separation to form a broad, central, spirally twisted tube extending down the middle of the body ; vitel- ligene and gennigene canals combining to form a simple oviducal canal, which is con- tinued into a simple uterine tube, finally opening near the lower margin of the ventral sucker ; eggs pointed at one end, or by a projecting spine near the hinder pole. Most helmintliologists agree as to the propriety of placing tliis remarkable trematode in a separate genus, but some dispute has arisen concerning tbe priority of the various titles wbicb. bave been proposed. The generic name here adopted is one which I applied to a second species (as I then supposed) discovered by me six months before Diesing communicated his " Revision der Myzelminthen" to the Vienna Academy ; but I shall have no objection to employ the title Gyncecophorus, proposed by him, if it be generally thought more appropriate. Weinland has expressed to me his willingness to abandon the title Schistosoma in favour of Bilharzia, which he 198 BNTOZOA. admits has the priority. Though it is of little consequence which name be retained, the genus itself is one of remarkable interest, not merely in a structural point of view, but also from its prevalence on the borders of the Nile, and also, according to Dr. John Harley, in South Africa and the Mauritius. The first specimens were discovered by Dr. Bilharz, of Cairo, in the portal system of blood-vessels ; and others were subsequently observed by him, Griesinger, Reinhard, and Lautner in the veins of the mesentery, bladder, and other parts, giving rise to a formidable and very common disease. This malady is likewise endemic at the Cape of Good Hope. On the 4th of December, 1857, 1 discovered a bisexual fluke of this kind in the portal vein of a Sooty Monkey (Gercopithecus) which had died at the Zoological Society's menagerie ; and, at the time, as well as for a considerable period since, I believed it to be a species distinct from the worm described by Bilharz. It was accordingly named Bilharzia magna. However, whilst I stiU retain the generic title which was then adopted, I do not now scruple to abandon the specific name, because I am fully inchned to agree with Leuckart that the two forms are identical. The disparity of size which then appeared to be a bar to their identity, does not in reality exist, since Leuckart has shown that some of the specimens derived from human sources were as large las the one which I found in the monkey. In any case the occurrence of this curious genus in the blood-vessels of man and monkeys is highly suggestive. It forms an interesting little circumstance, admirably suited to the taste of those who are on the look-out for afi&nities of habit between bimana and quadru- mana. The Gercopithecus fuligmosus is an African monkey, and, no doubt, in its native haunts it procures the larvae of Bilharzia from the same or from similar sources as those from whence our brethren in Egypt procure their larvas. Animals lower in the scale do not appear to be liable to attacks from this strangely organized genus of flukes, and, as yet, we are uninformed as to the hosts which entertain it in its larval condition. BILHABZIA HJ5MAT0BIA. 199 Up to the time of Bilharz's announcement of tlie existence of the Distoma haematobium, so abundantly found by him in the people of Eg3rpt, almost all the flukes were considered to be hermaphro- ditic, or, in other words, each individual was provided both with male and female organs: the only exception being that of the Distoma fiUcoUe, regarded by Rudolphi and Dujardin as a species of Monostoma. So common and numerous, however, is the Distoma hcematobium in Egypt, that Bilharz has expressed his belief that half the grown-up people are infested with it ; whilst, in 363 examina- tions of the human body after death, Griesinger found this entozoon present no less than 117 times. The latter authority also conjec- tures that the young of Bilharzia exist in the waters of the NUe, in the fishes which therein abound, or even in bread, grain, and fruit; but I think it is more probable that the larvae, in the form of cercarise, redise, and sporocysts, will be found in certain gasteropod molluscs proper to the locahties from whence the adult forms have been obtained. Our sooty host was, I understood, imported direct from its native country, and was not bred in the Society's gardens ; had it been otherwise, it would not, in all pro- babihty, have been infested by Bilharzia. The anatomy of Bilharzia has been described by the original discoverer, by Kuchenmeister, and especially by Leuckart; but before entering into particulars I take leave to note, in passing, that it is rather singular that Moquin-Tandon should express his behef that the sexes have been mistaken by such competent authorities. The circumstance of the smaller animal being care- fully described by them as ftimished with uterine ducts, containing eggs, ought to leave no doubt in our minds as to the correctness of the generally-received opinion, unless we have distinct evidence to the contrary. Without entering into minute anatomical details, there are several points which demand consideration. Taking the male first, one cannot fail to notice the horseleech-like aspect of the animal, due to the position of the oral sucker, the disk of which is placed almost on the same level as that of the ventral acetabulum. 200 ENTOZOA. The surface of the body is smootli in this region, but immediately below the ventral sucker the epidermis has a minutely tuberculated, warty aspect, which is continued onwards to the point of the tail. The pharynx is apparently unprovided with any special pouch, and there is no oesophageal bulb ; the tube bifurcates immediately above the ventral sucker, and these divisions passing on towards the region of the tail, reunite in the central line. The same thing occurs in the female, the point of union taking place much higher Fia. 44 — Bilharzia Ammatobia, Cobbold ; male and female, the latter partly enclosed within the gjnoecophoric canal. Considerably magnified. — Kuohenmeister. up in the body, and producing a long, tortuous, broad, and twisted central canal, which is continued to near the tip of the tail, where it terminates coecally. The testes appear to consist of several distinct lobes, or small oval organs, which are probably con- nected to a pair of vasa deferentia, opening externally by a single outlet below the ventral sucker. There is no evidence as to the existence either of a seminal pouch, or intromittent organ. In the female the viteUigene glands are situated, one on each side of the central intestinal pouch, whilst the egg-shaped ovary occurs near the point of junction where the intestinal divisions unite. From its posterior margin a germ-duct is given off, which unites with the ducts coming from the viteUigene glands ; and these together forming the oviduct are continued forward as a single uterine canal BILHARZIA H^MATOBIA. 201 up to the vaginal outlet, wMcli is directly below the lip of the ventral sucker. From BUharz and Leuckart I have taken most of these last-named particulars, since my original specimen from the monkey was a male. I have, however, also been enabled to confirm the truth of many other particulars given above, from a careful microscopic examiaation of the specimens which Leuckart has generously added to my private collection of entozoa. According to Bilharz the aquiferous system is represented by two thin canals, which unite to form a short, tubular " expulsion- sac," anterior to the central point of the tail, where there is probably an open foramen caudate. The eggs of BilJiarzia have been very carefully examined, and are rather peculiar. In the first place they are somewhat variable in outline, being usually more or less oval, pyriform, or sharply pointed at the hinder pole, but sometimes assuming a simply oblong figure, in which case they are furnished with a spine- like process placed at the side, and a httle anterior to the hinder end. Between these two type-forms other shght differences of outline also exist, but in all cases, whilst the eggs are still within the uterine canal, the hinder pole (or, in other words, that end of Fia. 45. — Eggs and embryos of Bilharzia hcematobia ; a, three ova (X 50 diam.), and a portion of mucous membrane with eggs attached (x 25 diam.) ; h. egg with segmented yelk ; a, free em- bryo ; d, ruptured egg, with embryo escaping (X 150 diam). — John Harley. the e^g which is opposed to the one ordinarily provided with an operculum) is directed towards the caudal extremity of the parent's body. Their size is likewise variable, presenting an average longi- tudinal measurement of about ^Js of an inch, and a breadth of ggo'- A true operculum does not appear to exist ; but Bilharz D D 202 ENTOZOA. saw tlie embryos escaping by a lateral slit near tbe anterior pole of tlie shell. Whilst the ova are still within the body of the parent, the embryos develop themselves into minute ciliated animalcules, and after their escape they exhibit Hvely movements. Many cihated embryos were found by Griesinger, free, in the intestine of the human subject. According to Bilharz and Leuc- kart, the embryos measure ^" in length, and ^" transversely. They are extremely delicate in structure, being, for the most part, transparent, and containing in their interior a quantity of fine, highly refracting, sarcode globules. At the anterior end, which is more or less pointed, Bilharz observed a double pyriform corpus- cular mass, which would probably represent the rudiments of a digestive pouch in the next stage of larval formation. Beyond this point, however, we know nothing as to the precise forms which the larvge of Bilharzia assume ; but it is, of course, highly probable that their sporocystic and cercarian features correspond, in the main, with those displayed by the larvEe of other trematodes. Injurious Effects upon Man. — The peculiar and formidable helminthiasis produced by this parasite has been thoroughly in- vestigated by Griesinger and Bilharz, and it is, hkewise, very fully described in the standard works of Kiichenmeister and Leuckart. The prevalence of the disease in Egypt has already been alluded to ; and its principal feature consists in a general disturbance of the uropoietic functions. Diarrhoea and hgematuria occur in advanced stages of the complaint, being also frequently associated with the so-called Egyptian chlorosis, cohcky pains, anaemia, and great prostration of the vital powers. The true source of the disorder, however, is easily overlooked unless a careful microscopic examination be made of the urine and other evacuations. If blood be mixed with these, and there also be a large escape of mucus, a minute inspection of the excreta will scarcely fail to reveal the presence of the characteristic ova of Bilharzia. Beside the increase of mucous secretion, there may even be an escape of purulent matter, showing that the disorder has far advanced. The whole BILHABZIA HJ!MATOBIA. 203 constitution eventually becomes undermined ; pneumonia often sets in, and death finally ensues. On making post-mortem exami- nations tte following pathological facts come to light. In cases where the disease has not very far advanced, minute patches of blood-extravasation present themselves at the mucous surface of the bladder, but in more strongly pronounced cases the patches are larger or even confluent. In some instances there are villous or fongus-like thickenings, ulceration and separation of portions of the mucous membrane, with varying degrees of coloration, according to the amount of the extravasation, which becomes converted into grey, rusty-brown, or black pigment deposits. A gritty or sandy deposit is often superimposed, consisting of the ordinary hthic acid grains mixed with eggs and egg-shells. Bilharz detected ova in the urine, these having probably escaped from the ruptured vesical vessels producing the extravasations and hsematuria. The lining membranes of the ureters and renal cavities are also more or less affected ; the kidneys being frequently enlarged and congested. It must, however, be borne in mind that in all these organs the true seat of the disorder is the blood, which forms the proper habitat of the Bilharzia ; and this being the case, the worms as well as their escaped eggs may be found in any of the vessels supplying the diseased organs. In one instance, quoted by Leuckart, Grie- singer found a number of empty eggs in the left ventricle of the heart, and from this circumstance it was supposed that they might be carried into the various important organs, or even plug up tho' larger vessels. As before stated, however, the parasites are more particularly prevalent in the vessels of the bladder, mesentery, and portal system. The effects upon the intestinal mucous mem- brane are, in most respects, similar to those occurring in the urinary organs. Blood extravasations, with thickening, exudation, ulcera- tion, and fungoid projections, appear in and upon the intes- tinal mucous and submucous tissues ; these appearances, of course, being more or less strongly marked according to the degree of infection. 204 BNTOZOA. The disease is said to be more virulent in the summer months, wMcli is probably owing to the prevalence of the cercarian larvae at the spring of the year. It makes very httle difference, however, as regards the prospect of cure, which, it need hardly be said, is extremely feeble after the disorder has once fairly set in. Here, indeed, remedies can be of little avail, the only treatment of any value, as regards the general loss of strength, being simply pal- liative and restorative. The great point to be aimed at is the discovery of the precise source of the higher larv« of the parasite ; and should it eventually turn out that these cercariae are limited to any one or two particular intermediate hosts, then, certainly, helmin- thologists would be in a position to show what precautions on the part of the people might secure them from the invasion of this fatal malady. At the same time, they would be able more cogently to enforce a recognition of the truism that " prevention is better than cure." Dr. John Harley, in his interesting paper on the hasmaturia of the Cape of Good Hope, has suggested the employment of diure- tics, but these remedies could be of httle avail since the seat of the disorder is in the blood. His Distoma capense is certainly iden- tical with Bilharzia hcematobia, and the symptoms produced by it are, for the most part, similar to those above described. A refer- ence to his cases wiU be found in the Bibliography. 7. Teteastoma benalb. T. renale, DeUe Chiaje ; Diesing ; Dubini ; etc. The occurrence of this entozoon as a human parasite appears hitherto to have escaped the notice of English zoologists, although discovered by Lucarelh in 1826, and described by Delle Chiaje in 1833. All that we now know of it is due to the original descrip- tion of Chiaje, from whose " Elmintografia Umana" we learn that it attains a length of five lines, has an oval flattened body, and is furnished with four suckers disposed in a quadrate manner at the HBXATHYEIDIUM PINGUICOLA. 205 caudal extremity. The reproductive orifices are situated near the mouth. The Tetrastoma is stated to infest the tubes of the kidney, but the evidence on which this statement rests is not altogether satis- factory. According to the original account given by Lucarelli, the patient iu whom this parasite occurred was a woman upwards of sixty years of age, and resident at Oapodimonte. She had symp- toms of calculus, with highly-coloured urine, in which latter there were deposited some small yellowish bodies. They exhibited a definite form, and were apparently organized. Altogether five specimens were collected for examination, when they showed signs of life. LucareUi also adds : — " After minute investigation, I thought that these creatures were tetrastomes, to which I applied the epithet renal, in accordance with their presumed habita- tion." At the expiration of two months the patient died, and on a post-mortem examination being made, no more tetrastomes were found either in the kidney, or in the urinary bladder. The renal organ was slightly enlarged. 8. Hexathteidium pinguicola. E. pinguicola, Treutler ; Jordens ; Brera ; etc. Hexastoma pinguicola, Ouvier. Linguatula pi/nguicola, Lamarck. Poly stoma pinguicola, Zteder ; Rudolphi; Bremser ; etc. This species was once foxmd by Treutler in a tumour about the size of a nut, which was connected with the left ovary, and no second instance of its occurrence, either in Germany or elsewhere, has since been recorded. The. original figure and description given by Treutler have been copied in various works ; and from these records we gather that this trematode attains a length of eight lines, the body being flat, somewhat hourglass-shaped in outline. 206 ENTOZOA. obtusely rounded in front, and produced behind, so as to form a conspicuous, tail-like appendage. At the anterior and ventral aspect of the head there are six small orbicular pores, serially dis- posed in a semilunar form, and there is also a sucker-hke organ situated in the central Hne about the root of the tail. A small opening is described as existing at the caudal extremity. Van Beneden and Gervais have supposed that this parasite may, after all, turn out to be the well-known Pentastoma denticulatum. This view, however, is quite inadmissible, as one may perceive from a consideration of the size, shape, want of claws, and, more especially, from the presence of a ventral acetabulum in Hexathyridium. 9. Hexathyridium yenabum. H. venarum, Treutler; Jordens; Rudolphi; etc. Hexastoma venarum, Ouvier. Hexacotyle venarum, BlainviUe. Linguatula venarum, Lamarck. Polystoma sanguicola, DeUe Chiaje ; Frick. P. venarum, Zeder ; Rudolphi ; Dujardin ; Owen; etc. This species is better known than the above. Treutler origi- nally obtained two specimens from the blood of the anterior tibial vein of a young man who accidentally ruptured the vessel while bath- ing, at Leipsic. Rudolphi and others sought to throw doubt on Treutler' s observation, and referred these worms to the fresh- water Planarice. At Naples, however, Delle Chiaje subsequently procured specimens from the sputa of two young persons suffering from hgemoptysis ; and a fourth instance also appears to have been noticed by FoUina, where the worm occured in venous blood. This species attains a length of three hnes, is cyhndrico-lanceolate in shape, its six suckers being biserially disposed on the under side of the so-called head. Davaine in his " Traite," previously quoted, gives Treutler's original description at ftiU length ; but, notwith- HEXATHYBIDTUM VENAEUM. 207 standing the nature of the facts recorded, he ventures to suggest that this -worm is neither more nor less than the Distoma lanceola- tum, or a young Fasciola hepatica. In this opinion I cannot coincide. ^ ' -'^'^?^ig?^X^f^^-^^^'^ 208 ENTOZOA. CHAPTEE IV. CBSTODA. General considerations respecting the origin of human tapeworms — Kuchenmeister's great merit in establishing the experimental method of research — The inferences of MM. Pouchet and Verrier successfully opposed by Van Beneden — Tcenia solium— General and specific characters — Name and history — ^Anatomy of the strobile and proglottis — Egg and six-hooked embryo — Measle or Cysticercus cellulostB. We now enter upon tlie consideration of ttose species of tlie great Cestode group of lielmintlis -wMcli are liable to infest the human frame ; and here it is that we encounter a series of strangely con- stituted beings, whose development in our bodies is fraught with the most disastrous consequences to health and life. Into the his- torical part of our subject I do not care to enter at any length, but those who are minded to acquaint themselves on this poiat can easily do so by procuring a copy of the " Conversations Jahrbiicher" for 1863, in which they will find Leuckart's admirable resmne of aU the principal data bearing on this curious subject.* In justice, however, to those who threw most light upon the helminthological obscm-ities of the past, I may remark that Dujardin, Bschricht, and Yon Siebold were the first to show that the cystic worms (hydatids, acephalocysts, etc.) were only phases in the life- development of the cestoda or tapeworms ; but the greatest merit is undoubtedly due to Ktichenmeister, who founded the experimen- tal method of demonstrating these relations. As Leuckart remarks, it was Kiichenmeister who first " hit upon the idea of administering * " Die neuestem Entdeckungen iiber mensohliche Eingeweidewurmer und deren Bedeutung fiir die Gesundheitspflege," s. 627. TiENTA SOLIUM. 209 the measles as provender to other animals, and of studying the changes which took place in the alimentary canal of the quadrupeds thus fed. Such a trial might, it is true, very naturally suggest itself to any one, but this does not lessen the merit due to Kiichen- meister, seeing that the result was thoroughly decisive." These experiments gave a new impulse to the study of helminthology, which was now pursued with avidity by several workers co-operat- ing with Kiichenmeister, and also by others acting independently, amongst the more prominent of whom one may especially particu- larize Van Beneden of Louvain and Leuckart of Giessen. From the very nature of the experimental method adopted, it was easy to perceive that occasional errors of interpretation would be liable to occur, even in the minds of those who had enjoyed con- siderable experience in helminthological pursuits conducted after the fashion pursued and systematized -hj Eudolphi. Von Siebold especially erred in this manner, disputing Kiichenmeister's well- ascertained results, and throwing down a gauntlet which in later times has been taken up by others. Thus, not long ago, MM. Pouchet and Verrier gave a general denial to the opinions of expe- rimental parasitologists respecting the development of tapeworms from Gysticerci. Those who have read the statement, as presented in the " Comptes Kendus" (for May 6th, 1862, p. 958), or the translation of it given in the July number of the " Annals of Natu- ral History" (3rd series, vol. x. p. 77, et seq.), wUlat once perceive the causes which have led these gentlemen to form conclusions at variance with the experience of at least nine-tenths of the leading helminthologists of the day. As Professor Van Beneden remarks, they err greatly in supposing that any one regards the Goenwrus of the sheep as the larva of Tmnia serrata of the dog, seeing that nearly all Continental experimentalists, following Kiichenmeister, have maintained that the scolex condition of this last-named tape- worm is unquestionably the Gysticercus pisiformis of hares and rabbits. The researches of Leuckart are especially conclusive on this point ; and my own experiments at Edinburgh in 1856, together E E 210 ENTOZOA. with others since recorded, have left no doubt in my mind as to the correctness of this view. The negative result obtained by MM. Pouchet and Verrier in their last experiment (where they fed two dogs, each with a hundred heads of Goenurus cerebralis) cer- tainly seems contradictory as regards the Tcenia coenurus ; whilst, on the other hand, it tends to confirm the correctness of the generally received opinion that Goenurus cerebralis and Tcenia serrata have no genetic relation subsisting between them. Into this dis- cussion, however, it is quite unnecessary in this place to enter any further. We may, I think, confidently conclude that the few diffi- culties which still prevent a uniform adhesion to the current opinions of the day, will, in due time, be satisfactorily explained. 10. T^NTA SOLIUM. T. solium, Linneus ; Grmelin ; Rudolphi ; etc. T. solium (var. abietina), Weinland. T. osculis marginalibus solitarius, Linneus ; Bradley. T. cucurbitina, Pallas ; Bloch ; Batsch ; Sohrank. T. cucurbitina plana pellucida, Goeze. T. humana armata, Brera. T. lata, Pruner. T. degener, Spigel. T. dentata, Gmelin. T. fenestrata, Chiaje. T. vulgaris, Werner. T. commv/nis, Moquin-Tandon. T. albopuMcta hominis, Treutler. T. hydatigena anomala, Steinbach. T. hydatigena suilla, Fabricius. T. finna, Gmelin. T. cellulosa, Gmelin ; Treutler. T. e capite bonce spei, Kiichenmeister. T. capensis, Moquin-Tandon. T^NIA SOLIUM. 211 General and Specific Characters. — ^A large species of cestode helminth, in its sexually- mature or strobila corLdition, varying from ten to twenty, or even, it is said, to thirty feet and upwards in length ; breadth at the widest part very nearly one-third of an inch ; head about the size of a pin-cap, globular, but produced in front so as to form a short. Conical proboscis or rostellum, the latter being armed with a double crown of hooks, from twenty-two to twenty-eight in each circular row, head furnished with four sucking disks, and succeeded by a very narrow neck nearly half an inch in length ; the latter being continued into the anterior, front, or sexually immature part of the body, in which traces of segmentation at first appear in the form of fine transverse lines, which gradu- ally becoming more and more widely separated, leave brief interspaces ; these parts merging eventually into distinct segments or joints ; the earliest formed immature joints are extremely narrow, the proglottis or sexually -mature joint commencing at about the four hundred and fiftieth segment (Leuckart) ; the total number of joints in a worm ten feet long being upwards of eight hundred (Kiichenmeister) ; mature proglottides twice as long as they are broad, comparatively thin and transparent, furnished with a branched uterus, consisting of a central longitudinal stem, giving off from seven to ten branches on either side ; joints in the form of herm.aphroditic zooids, having a common reproduc- tive papilla, placed at the border on one side below the central line, but not uniformly either to the right or left in series ; male orifice in front or above the vaginal outlet ; penis sickle-shaped ; eggs rounded ; larval or hydatid condition equivalent to the well- known measle or Cysticercus (telee) cellulosee of authors. Name and History. — Not a few persons still suppose that the common tapeworm occm-s solitarily in the human body, being naturally led into this error by the Linnean title, which certainly was originally intended to convey a notion which we now know to be erroneous. Frequently, indeed, it occurs singly, but Kiichen- meister has several times found two or three together ; his col- league. Dr. Pfaff, saw seven ; Madame Heller thirty ; and Kiichen- meister adds, " Dr. Kleefeld of Gorhtz once counted forty expelled from one patient." In many cases, where it has been said that one enormous long worm existed, it is more than probable that there were several associated. Thus, in Dr. Cofl&n's American edition ofBrera's "Treatise on "Verminous Diseases," which has also been quoted by "Weinland, " Van Doeveren relates the history of a pea- sant who, after taking an emetic, evacuated sixty metres (upwards of sixty-five yards) of Taenia, and who probably would have voided more if he had not broken the worm from an apprehension that he was discharging all his intestines." One can scarcely believe this was a single specimen of Tcenia solium. The tapeworm in its strobile condition has been known from 2] 2 ENTOZOA. the earliest times, though possibly not earlier than the measles, from which the worm originates. Hippocrates, Pliny, and Aris- totle described the fiiU-grown worm ; and, in regard to the larvae, some have gone so far as to express their belief that the prohibition of swine's flesh as food amongst the Jews and other Oriental people, was dictated by sanitary considerations. Weinland suggests that the Mosaic commandment not to eat pork might have originated in an old popular notion " of the fact that tapeworm sometimes comes from this food." Certainly, one must admit the possibility of the truth of Weinland' s hypothesis ; for, if one supposes Moses to have been supernaturally informed that (measly) pork would produce tapeworm disease among the people, one naturally asks why veal and beef should not also have been prohibited, seeing that these meats also harbour tapeworm larv^, nearly as frequently as pork. Anatomy. — Now that the general organization and mode of development of this species is so well understood, it is a matter of regret that the manifest errors of earlier writers are not more care- fully excluded from our ordinary manuals of zoology and compara- tive anatomy. I allude, for example, to such points as the stUl asserted presence of a mouth and digestive canal in the Tcenia, which cannot be maintained, since repeated demonstrations have clearly proved this view to be erroneous. These falsely so-called alimentary canals constitute the water-vascular system which will be briefly described below. I say " briefly," because the hmits and design of this work will not permit me to give excessively minute anatomical details. The head of Taenia soliwm is seldom seen in our pubhc anato- mical museums, although the evacuation of entire adult tapeworms is not of very rare occurrence. Placed under the microscope, it displays, in addition to the characters already mentioned, a quan- tity of dark, almost black, pigment granules, which are particularly abundant at the base of the rostellum, and in the neighbourhood of the hook sacs. They exhibit a bright crystalline aspect, and vary somewhat in quahty ; this proportion, however, being neither TiENIA SOLIUM. 213 dependent on age nor situation. They are equally present and abundant in tlie pork-measle, and in the specimens of Gysticer- cus cellulosce derived from the human subject. The cephalic hooks of this cestode are comparatively large, those of the greater series measuring as much as jjo', whilst the smaller have an extreme length of about 220 '. The sharp thorn-hke extremities of the hooks of both circles terminate outwardly at a common point of distance from the centre of the rostellum ; so that a line carried from point to point, in succession, will indicate the circumferential limit of the double crown, forming, in fact, a simple circle. The roots and Fig. 46. Fragment of the strobile of Tcenia solium, Linneus ; showing, more particularly, the reproductive apparatus and water ressels of a single proglottis. — Bokitansky. stems of the hooks are received into a corresponding double series of socket-like pouches, which are visible even when the hooks them- selves may be wanting. They were, I beheve, first accurately de- scribed by Kiichenmeister. The tegumentary covering of the head differs in no important particular from that of the rest of the body, displaying an external thin, smooth, transparent, chitinous epidermis superimposed on a rather thick, fibrous corium. Beneath the 214 ENTOZOA. latter, there are layers of longitudinal and transverse muscular fibres, pervaded by a great quantity of so-called calcareous corpus- cles. These oval bodies, about which more will be said hereafter, also occur in the corium, but not in the cuticular layer. Beneath these structures, in the mature segments, we find a dense layer of parenchyma, which forms a Hmiting membrane, within which is enclosed the central reproductive mass. This latter consists of an anterior testicular group of elements, and a posterior uterine group. The former, in place of a simple testis, consists of a number of small vesicles or sacs, in which filiform spermatozoa have been detected ; these latter, when ripe, being conducted by a vas deferens into a seminal pouch from which a canal passes laterally into the penis; the latter organ, in its retracted condition, being lodged within a flask-shaped sheath or cirrhus-pouch. The female organs are some- what more comphcated. They consist of two masses of viteUigene glands occiipying a limited space, a small ovarium, a centraUy- placed and largely-developed branched uterus, canals of outlet lead- ing from all these organs, and enlargements of the main passages to form internal seminal reservoirs ; also, a vaginal canal, which is widened at its termination to form a receptaculum for the curved penis. These several parts, as weU as their development, have been ably determined and investigated by Leuckart, to whose well-known treatise I must refer those who desire more minute details. In addition to the above-named structures, the entire series of joints ff om the head downwards are traversed by a set of vascular canals, which are doubled in the region of the head. These consti- tute the so-called aquiferous system. It is usually described as consisting of two main channels, one passing down on either side of the worm, and both being connected by transverse vessels, which occur singly at one end of every joint. This statement of their arrangement is substantially correct ; and without entering into minute details, I may here remark, in passing, that they do not form tubes of uniform thickness throughout their course, but pre- sent distinct bulbous enlargements at every joiat, where the trans- T^NIA SOLIUM. , 215 verse brandies are given off. This I have recently ascertained from the careful injection of a perfectly fresh tapeworm. In the neigh- bourhood of the head the two channels divide to form four distinct vessels, which, according to Kiichenmeister, " are united quite at the front of the head by a common transverse branch, as thick as, or thicker than, themselves." Kiichenmeister also thought he re- cognized the existence of cilia mthin these canals, such as have undoubtedly been shown by Van Beneden, Virchow, Wagener, and others, to occur in allied cestodes. The eggs of Tcenia solium in their mature condition present a globular figure, and are easily recognized by their remarkably thick Fj&, 47. — Eepresentation of the mode of union of the lateral and transrerse vascular trunks in Tcenia solium ; outlined with the aid of a camera (x 40 diam.) — Original. shell, which surrounds the contained six-hooked embryo, leaving a brief interspace between the surface of the latter and the inner layer of the shell. They present an average diameter of -555 of an inch, the shell itself measuring about ^" in thickness. As early as the year 1856 I observed that many of the eggs, whilst still within the uterine branches, displayed an outer envelope, very delicate in structure, and totally dissimilar from the egg-shell proper. This has since been more accurately described by Weinland, and espe- cially, also, by Leuckart, who has, moreover, given a minute account 216 ENTOZOA. of tte development of the ova and embryos from their earliest commencement. The outer membrane, according to the latter authority, constitutes the primitive yelk-membrane, within which a part of the yelk-contents separate to form the true egg and em- bryo by a process of daughter-cell formation ; the other part of the yelk remains as a granular mass, being concerned, possibly, as an organ for secreting the true chitinous shell (Fig. 4, Plate ^11). When the true sheU is fully formed and the outer layer is still in exis- tence I have observed this granular mass to be altogether absent, Weinland describes a second delicate or middle membrane within the outer one (in Hymsnolopis), but this may be only the surface of the coagulated contents, which, in addition to the well-defined granular mass, consists of loose granules floating in a clear albu- minous fluid. The true shell displays a series of radiating and cir- cular hues ; the former, however, are more conspicuous than the latter, being due, according to Leuckart, to the presence of a series of fine rod-like chitinous elements, which are formed on the exter- nal surface of the original true shell membrane. The enclosed embryo presents a simple granular aspect, and is furnished with six boring spines, arranged in three pairs, the whole being invested by an extremely delicate skia-membrane, which is separated from the inner surface of the shell by a clear transparent fluid. The embryo measures j^" in diameter. Leaving the consideration of the measle as a disease for sub- sequent notice, I now proceed to glance at the so-called scolex or larval condition of this tapeworm, which in its most complete stage of development constitutes the weU-known Gysticercus (telce) cellulosce of authors. Its earlier stages of growth have been ably worked out by Leuckart. In this kind of investigation, it is true, he was anticipated by Eainey, but it may be reason- ably doubted if the minute corpuscles described by Eainey as representing " the earliest indication of this species of Gysticercus" have anything to do with the measles whatever. It unfortunately happens, also, that the so-called Raineyan sacs with their con- i'i.A'J'K AW. Iceiija sohum, Luirjseus. JJler Ulauchard, Leuckart, and .Smi/h. T^NIA SOLIUM. 217 tained corpuscles had been previously described by Hessling, who discovered them in the muscular fibres of the heart of the sheep, ox, and roe.* They were regarded by him as granular masses formed by the disintegration or breaking up of the muscular sub- stance, but Leuckart thinks it more probable that they are organized structures comparable to the so-caUed sacs of Psoro- spermise. The smallest measles found by Leuckart measured as much as ^" in length, being obtained from the brain, hver, and intermuscu- lar substance of a pig fed with tapeworm proglottides about thirty days previously. Only those specimens, however, occurring in the liver at this early period, displayed an outer membrane proper to the worm itself, the others being simply invested with capsules formed out of the surrounding connective tissues belonging to the host. Many measle masses in the same host were much larger, presenting an average diameter of |". The smallest of the above- mentioned already displayed a smooth, transparent, homogeneous, outer, cuticular membrane, overlying a double, finely-granular corium ; the latter being traversed by a branched system of aquife- rous vessels. These vessels proceed fi:-om a central spot, which marks the position of the so-caUed head-cone or receptaculum capitis. It is, in fact, the first well-marked indication of that flask-shaped capsule within which the head, neck, and body of the Cysticercus is formed, and which Groeze long ago very aptly com- pared to a lantern (Figs. 6 — 10, Plate XII). As growth proceeds, a very interesting series of changes takes place within this cavity, by virtue of which these several parts, as well as their own distinctive organs, are continuously brought into view. A central granular mass forms the true foundation of the head, its upper or stalk-like extension forming the future neck and body. Fm-ther develop- mental changes (into the minuter particulars of which the limits of this work forbid me to enter) successively result in the evolution of * Siebold and Kolliker's " Zeitschrift," Bd. v. 1853. See also Leuckart ; s. 240. F P 218 ENTOZOA. the internal water-vascular system, the calcareous corpuscles, the marginal transverse foldings of the body, the four suckers, the ros- teUum, and, in particular, the double coronet of hooks. All these metamorphoses have been minutely investigated and described by Leuckart, who also finds that the complete development of the Cysticercus cellulosoe is ordinarily accomplished within the space of ten weeks. In its highest grade of formation, the Gysticercus cellulosce, or pork measle, presents the appearance of an elliptical or reniform hydatid, varying in size from that of a pea to that of a small kidney-bean. The measles present an average diameter of g", but some exceed this considerably. The vesicle displays a more or less opalescent appear- ance, the density being much increased at the side where the head and neck is lodged within the so-called rec&ptaculum, or Groeze's lantern (Figs. 11 — 13, Plate XII). If one such measle be dissected or broken up, it will be immediately perceived that the great vesi- cular portion constitutes the bladder-like caudal extremity of the Cysticercus, whilst the head, neck, and body can be drawn out so as to exhibit a vermiform character. Even before the vesicle is injured, one can readily perceive that these last-named parts lie coiled within the receptaculum in a spiral manner. The neck and body display a series of tolerably regular transverse folds, and on microscopic examination, the cephalic hooks, suckers, and calcare- ous corpuscles are readily brought into view. The hooks, about twenty-four in number, have each a straight shaft, a barb-like anterior root, and a claw-like, sharply-pointed extremity; in other respects they resemble those of the adult tapeworm. In like manner, the calcareous corpuscles, which Smith erroneously designated assimilating cellules, present appearances very little dif- fering from those seen in the full-grown animal. They consist of clearly-defined, circular, oval, elhptic, oblong, or reniform disks, measuring, according to Smith, from ^" to i^" in diameter. Their more intimate structure and nature will be found fully dis- cussed elsewhere in this work. As regards the general structure TiENIA SOLIUM. 219 of the Oysticercus, I need scarcely add that no trace of diges- tive or other internal organs can anywhere be distinguished ■within the body, whilst the caudal vesicle itself is simply distended with a clear, transparent, albuminous fluid. 220 ENTOZOA. CHAPTER V. T^NIA SOLIUM. Development of the common tapeworm — The life phases of Tisnia solium regarded as parts of the " zoological individual " — Injurious effects upon man — Particular instances — Frequency of Oysticeroi in the human brain — Mr. Hulke's case — Pre- cautions suggested — Statistics — Treatment. Having devoted an entire cTiapter to the consideration of the general characteristics and structure of the common tapeworm, both in its adult and larval conditions, I proceed, in as brief a man- ner as possible, to give an epitomised view of the developmental changes and wanderings which are undergone by this species in its passage from the free proglottis condition into the ordinary, sexu- ally mature Tcenia solium. A part of these life-changes have been indicated already, but their intermutual relations have now to be described and explained under a separate head. Development. — After the proglottis (which, it must be borne in mind, is furnished with male and female reproductive organs) has undergone impregnation by contact with another proglottis, there results from this the formation of eggs within it, which eggs, whilst still within the body of the parent, develop into embryos, the latter still retaining the egg coverings. At this time the pro- glottis is about to undergo a passive migration, and having de- tached itself from the strobila, it is soon expelled from the bowel of the host, thus finding its way into some cesspool, or, it may be, into the open fields. The proglottides move about for a time, but the growth of the multitude of embryos within their interior causes the TiENIA SOLIUM. 221 proglottis sooner or later to burst, and the embryos thus become dispersed ; some are thus conveyed down drains and sewers, others are lodged by the roadsides in ditches and waste places, whilst great quantities are scattered far and wide by winds or insects in every conceivable direction. Each embryo is furnished with a special boriug apparatus, having at its anterior end three pairs of hooks ; the entire group of embryos of any single proglottis is consequently called the " six-hooked brood." After a while, by accident, as it were, a pig coming in the way of these embryos or of the proglot- tides is liable to swallow them along with matters taken in as food. The embryos, immediately on their being transferred to the digestive canal of the pig, escape the eggshells and bore their way through the living tissues of the animal, and having lodged themselves in the fatty parts of the flesh, they there rest to await their further transfor- mations or destiny. The animal thus infested become measled, its flesh constituting the so-called measly pork. In this situation the embryos drop their hooks or boring apparatus and become trans- formed into the Gysticercus cellulosce. A portion of this measled meat being eaten by ourselves, either in a raw or imperfectly cooked condition, transfers the Gysticercus to our own alimentary canal, in which locaHty the Gysticercus attaches itself to the wall of the human intestine, and, having secured a good anchorage, begins to grow at the lower or caudal extremity, producing numerous joints or buds to form the strobila or tapeworm colony. Thus the cycle of life-development is completed, and we have a simple alternation of generation in which the immediate product of the proglottis (or sexually-mature zooid-individual) is a six-hooked brood ; by metamorphosis the latter becomes transformed into the Gysticercus, having a head with four suckers, and a double crown of hooks ; and by gemmation the latter gives rise to a whole colony (strobila) of individuals, the greater part of which are destined to become sexually mature zooid-individuals, or proglottides. It will be observed, therefore, that the product of a single ovum is, in the first instance, a single non-sexual embryo ; in the 222 ENTOZOA. second phase, it becomes a non-sexual Cysticercus (these two phases together constituting the protozooid) ; in the third change it gives off, by budding, numerous gemmules, most of them des- tined to be sexually-mature individuals (or deuterozooids), in this way resembling their original parents.* As I have already attempted to show in the case of Taenia serrata, the relation and nature of these developmental changes may be farther simpHfied by placing the various life phases in a tabulated form, as follows : — a. Egg in all stages. ^ b. Six-hooked embryo = prosoolex. / . , e. Eestiag larva or Cysticereus (telts) C Zoological Indivldtjai ■ . . { cellulosce (scolex). J d. Immature tapeworm. e. Strobila, or sexuaUy-mature T