THE LIVER-FLUKE OF SHEEP. 



74i 



utable, by those who maintain the germ-theory in disease, to atomic 

 germs. The number of disease-germs does not matter, as is evidenced 

 by the communication of disease by letter where the number must 

 necessarily be limited. The atomic dose is but a stimulus to Nature. 

 Nature cures, aided or unaided. The atomic dose but excites in a 

 greater degree those powers of reaction and resistance of Nature al- 

 ready set in motion by disease which is a disturbing cause. Nature 

 always seeks to restore the equilibrium of her forces. 



-"-- 



THE LIVER-FLUKE OF SHEEP. 



By BYKON D. IIALSTED, Sc. D. 



THE object of this paper is to briefly summarize the present knowl- 

 edge of the liver-fluke, causing the much-dreaded and fatal 



rot " in sheep. Professor A. P. 



Thomas, 



of Balliol College, Ox- 



7 , 

 ,,-y 



miij(|:'H ; \ 



ford, has completed his long and extended researches on this parasite, 

 which have been carried on under the direction of the Royal Agricul- 

 tural Society of England. Professor Thomas's 

 concluding report appeared in the last issue of 

 the " Royal Agricultural Journal," from which 

 the leading facts here given are drawn and the 

 engravings borrowed. 



The liver-fluke, shown twice the natural size 

 in Fig. 1, is a sucking-worm related to the com- 

 mon leech, and known to zoologists as Fasciola 

 hepatica. It has the shape of a privet-leaf, is 

 pale brown or flesh-colored, and from an inch 

 to an inch and a third in length. There is a 

 short projection at one end, and at its tip, y, is a 

 sucking-mouth by which the fluke can attach it- 

 self to the surface of the bile-ducts of the sheep. 

 A second sucker, y', is situated at the place where 

 the head joins the body. These flukes are found 

 in abundance in the livers of sheep and other 

 animals infested with the " rot," and produce 

 vast numbers of eggs. Each of these eggs 

 under proper conditions gives rise to an animal 

 " which is never like its parent, never does be- 

 come like it, and never lives where its parent 

 lives." It will be seen that in the liver-fluke we have an example of 

 what is known among naturalists as an alternation of generations. 



The eggs, one of which is shown in Fig. 2 very highly magnified, 

 are about -$fa of an inch in length, but may be made visible to the 



Fig. 1. 



