PARASITOLOGY. 173 



bryo finds a resting place. From this small mass of 

 protoplasm is developed first an acephalo cyst, 

 which is provided with two membranes, the outer 

 one called the hydatic membrane and the inner one 

 called the germinal membrane ; from the germinal 

 membrane there is developed the larva ; this consti- 

 tutes the fully developed larval state. The cyst is 

 oval in shape and about one-half to two-thirds the 

 size of a navy bean ; the larva can be seen through 

 the cyst wall as a small white body and consists of 

 the head, provided with four sucker discs and twenty- 

 four to thirty-two booklets arranged in a double row. 

 This head or larva is attached to the inner or ger- 

 minal m.embrane by means of a pedicle and floats in 

 a colorless fluid ; each cyst contains but one larva. 

 The cyst is fully developed in sixty days ; it infests 

 voluntary, involuntary and heart muscles, and the 

 glands and organs of the body, invading the cancel- 

 lated portion of bone. After cysts are quite old they 

 undergo degeneration, beginning from without to 

 within ; through this degeneration process the cyst 

 wall may rupture and and cyst collapse, or it may 

 become filled with a cheesy or earthy material. 

 Should man eat the meat of the hog infested with 

 the cyst containing the living larva, through diges- 

 tion the larva is liberated and finds its way to the 

 small intestines and fixes itself to the mucous mem- 

 brane by means of its booklets and four sucker discs, 

 and develops into the mature form. 



Animals Infested. — Man, hog and dog. 



Parts Infested. — Adult infests the small intestines 

 of man. The larval form infest the muscle structure 

 of the hog and sometimes the dog, in cyst formation. 



