CHAPTER LXXYI. 



PAEASITIC DISEASES,— continued. 



CESTODA. 



The most important diseas.e of stock caused by this order of 

 parasites is that variously termed 



STUKDY, TURNSICK, OR GID. 



This is a species of vertigo induced by the Gcenurus cerehralis, 

 which is the hydatid or larval form of the tape-worm, called the 

 Taenia ccenurits. Many conclusive experiments have been made 

 in this and other countries, recorded in works on helminthology, 

 which proves that the mature Tccnia coenurus infests the intes- 

 tines of the dog, from which perfect segments are expelled. 

 These segments, falling on the pastures where sheep are feeding, 

 are swallowed along with the herbage, and, as explained by Dr. 

 Cobbold, the six-hooked embryos, escaped from the ova con- 

 tained in the segments, commence their wandering in the tissues 

 of the higher animal, and, by virtue of their selective capacity, 

 escape from the blood-vessels of the brain, and bore their way to 

 their final resting-place in that organ. Even when the hrsdn is 

 reached, it by no means follows that every embryo attains its 

 full growth. Indeed, it is only usual for one to flourish, some- 

 times two of equal size, but seldom more. It has, however, been 

 observed that when one hydatid cyst has been removed, that 

 another has developed in a different part of the brain. This 

 proves that the brain serves as a proper habitat to one or at 

 most to two hydatids at a time. 



This disease attacks cattle as well as sheep, but in this country 

 it seldom attacks any but sheep, its victims being lambs under 



