188° PARASITOLOGY. 
pores irregularly alternate; the ripe segments are 
nearly twice as: long as wide... The worm usually 
attains the length of two to three feet. | 
_ Lite Cycle.—The ripe segments from the small in- 
testines of the dog pass out to the ground with the 
feces; these segments soon decompose and myriads of 
ova are liberated which become desseminated in food 
and water. The intermediate host is sheep which 
become infested through contaminated food or water. 
The ova, upon reaching the stomach, hatch into six- 
hooked embryos which immediately begin to migrate 
through the tissues, or they may penetrate an artery 
and be carried by the blood current; the embryos 
will develop only in nerve tissue, and may be 
carried to these centers through the blood stream; 
if lodged in tissue, not nerve, they perish,: but if 
lodged in the brain or spinal column they begin their 
transformation into the hydatic state; in eight or 
nine days after the ova are ingested the embryos 
have reached the brain and in twenty days are about 
one-tenth inch in diameter; development continues 
and they are fully developed in ninety days. The 
cysts possess a hydatic and germinal membrane ; 
from this inner or germinal membrane there is devel-. 
oped from one to two hundred heads or larva. The 
encysted larva is called Coenurus Cerebralis or 
Cysticercus Coenurus. They may develop in the 
coverings of the brain or spinal cord or in the brain 
and cord. substance; if the dog eats these cysts, 
through digestion the larva (which consists ofa head 
provided with four sucker discs and a rostellum of 
hooklets and a neck) is liberated ‘and fixes itself. 
to the mucous membrane of the small intestines and. 
develops into the mature worm in two months. 
