172 POUCHET AXD VEURIER^ ON 



dog have attained tlieir full development, the rings which 

 they throw off are passed with the excrement, fall upon the 

 grass, and are swallowed hy the ruminant. Soon afterwards 

 the ova conta-'ned in these segments arc hatched in the 

 intestines of the sheep, giving birth to microscopic larvje, 

 which perform what may truly be termed a jirodigious 

 journey. From their native seat they force a route into the 

 interior of the head,, and, in the course of the journey, are 

 obliged to penetrate through the most various living tissues — 

 the base of the skidl even does not stop them. Instinctively 

 they find one of the openings, and tear through the resisting 

 tissue which fills it up. Having thus finally reached the 

 brain of the sheep, they take up their abode in it, and there 

 produce the Ccenwus by which the host will infallibly be 

 destroyed. This closes the cycle of existence of the helminth, 

 and the shepherd^s dog incurs the grave suspicion of infecting 

 the flock committed to his charge. 



Nevertheless, however great may be the complications 

 attending a migration of this kind from one animal to an- 

 other, and the subsequent journey through its tissues, if it is 

 shown actually to take place, however mysterious the pro- 

 ceeding may appear, logically we are bound to admit its 

 reality. But it is precisely at this point that we meet with, 

 we will not say insurmountable, but with, at any rate, enor- 

 mous difiiculties. Let us see what these are. 



The CiBmirus cei-ebralis, according to V. Siebold, Van 

 Beneden, and other naturalists, would be the larva of Taenia 

 serrata. But, on the other hand, this Tania serrata, ac- 

 cording to Kiichenmeister, Van Beneden, Baillet, and V. 

 Siebold himself, would appear to be the product of Cysticercus 

 pisiformis, or of Cysticems cellulosa, and C. tenuicollis, 

 according to what V. Siebold further says. 



Here we find ourselves in the utmost embarrassment. It 

 must be allowed, however, that zoologists have exhibited 

 great ingenuity in this matter, if they have not been very 

 exact. Immediately a T<Bnia is met with in any carnivorous 

 animal whatever, the evil is at once imputed to his victim. 

 The cat derives its worms from the rats and mice it devours ; 

 the wolf and the dog find theirs in the rabbits and sheep; 

 man is indebted to the pig. But a scrupulous examination 

 of the facts excites some doubts with respect to all this. It 

 may be asked, for instance, how is it that the sheep, which 

 does not eat the flesh of any animal, sometimes has its 

 intestine filled with such a multitude of Tcenice as to have it 

 completely .obstructed by them? In an epizootic malady, 

 which carried off" many sheep in the neighbourhood of Rouen, 



