148 ENTOZOA. 



General and Specific Characters. — A trematode helminth, usually about three-fourths 

 of an inch in length, but; occasionally measuring an entire inch or even fourteen lines, its 

 greatest breadth also varying from half an inch to seven or eight lines transversely ; 

 body very flat, presenting distinct dorsal and ventral surfaces, frequently curved toward 

 the latter during life ; upper or anterior end suddenly constricted, produced, rounded, 

 and pointed, forming the so-called head and neck ; posterior extrenaity less acuminated, 

 sometimes rounded, or even slightly truncated ; margins smooth, occasionally a little 

 undulated, especially towards the upper part ; oral sucker terminal, oval, rather smaller 

 than the ventral (acetabulum), which is placed immediately below the root of the neck ; 

 reproductive orifices in the middle line, a little above the lower sucker ; intromittent 

 organ usually protruded and spirally curved ; a central, hght-coloured space, extending 

 two-thirds of the body from above downwards, marks the region of the internal male re- 

 productive organs, being bordered on either side and below by a continuous dark band, 

 indicating the position of the so-called yelk-forming organs ; a small, brown-coloured, 

 rosette-like figure, placed directly below the ventral acetabulum, shews the limits of the 

 uterine duct ; a series of dark lines, branching downwards and outwards on either side, 

 marks the position of the digestive organs ; general colour of the body pale brownish- 

 yellow, with a slight rose tint. 



History. — This entozoon, familiarly called the liver-fluke, has 

 been known from the earliest times, and may almost be said to 

 have acquired a literature of its own. We have clear evidences 

 that it was described by Gabucinus in the year 1547, and also sub- 

 sequently by Cornelius Gemma, who, in a work published some 

 thirty years later, refers to an epizootic disease prevalent in Hol- 

 land during the year 1552, and which was very justly attributed to 

 the parasite in question. After this date many writers described 

 the hver-fluke more or less accurately, and entire volumes were de- 

 voted to the consideration of the formidable disease which it occa- 

 sions. In the recent work by M. Davaine, we are furnished with a 

 brief resume of the principal facts bearing upon the history of the 

 Fasciola, together with numerous references to ancient authorities ; 

 therefore, it is unnecessary here to do more than refer those who 

 desire further information on this subject to his excellent treatise.* 



Name. — The scientific nomenclature of this parasite involves a 

 question of some importance. Amongst naturalists, generally, the 

 common liver-fluke is continually described under the combined 

 generic and specific titles of Distoma Jiepaticum ; but working para- 

 sitologists, who are at the same time acquainted with the writings 



* " Traite des Entozoaires, et des Maladies Yermineuses," etc. p. 235, et seq. Par C. 

 Davaine. Paris. 1860. 



