124 ENTOZOA. 



The Gysticercus tenuicollis enjoys an unusually wide distribution, 

 for in addition to its occasional presence in man, it has likewise 

 been found in various monkeys, in cattle and sheep, in several other 

 ruminants, in horses, in swine, and, it is said, in squirrels. Ordinarily, 

 this larva acquires the size of a pigeon's egg, but in certaiti cases 

 the caudal vesicle attains the bulk of a cricket-baU. Sometimes the 

 vesicle is perfectly spherical, at other times it is elongated and pyri- 

 form. The head is famished with a double crown of hooks, and is 

 succeeded by a short filiform neck which expands more or less sud- 

 denly into a tolerably thick body, marked by numerous fine trans- 



Fia. 26. — Head of Cysticereus pisiformis (X 50 diam.) ; from the rabbit. — Drawn from a pboto- 



graph taken by Dr. Hallifax. 



verse lines. The transition from the lower part of the body into the 

 caudal vesicle is occasionally very sudden, and at other times very 

 gradual. I have foimd a remarkable example of the former kind, 

 where the parasite was lodged in the abdomen of a Wart Hog (Phaco- 

 chcerus CBthiopicus) , and a scarcely less remarkable illustration of the 

 latter in a Red River Hog (Potamochcerus penicillatus). In the 

 last-named animal one larva occupied a cyst in the liver, four 

 others being attached to the mesenteric folds of the peritoneum. All 

 five bore a close resemblance to one another, but they difiered very 

 materially from the Gysticercus infesting the Ethiopian Wart Hog. 



