290 PARASITES OF THE DOMESTIC ANIMALS 



ing water or perhaps with green forage. Reaching the intestines, they 

 penetrate the mucosa from which probably the majority of them reach 

 the circulatory system where the}^ become lodged in the visceral arteries, 

 as the trunk of the great mesenteric. After a variable time in this 

 location they again enter the blood stream and, reaching the cecum, 

 oecome encysted in the submocosa where their development proceeds. 

 Within the cyst they possess a buccal capsule and a caudal bursa, but 

 the generative organs are not as yet developed. 



Finally they pass to the lumen of the bowel where they attach to the 

 mucosa and acquire all the characters of the adult. Copulation then 

 takes place, the eggs are deposited, and a new generation repeats the cycle. 



Symptoms. — The symptoms brought about by the presence of these 

 worms — a condition generally known under the name of sclerostomiasis — 

 are not characteristic and vary according to the location of the parasites. 

 The presence of the adults upon the mucosa of the cecum, even in con- 

 siderable numbers, rarely .causes serious disturbance, diarrhea and 

 occasional attacks of colic resulting in exceptional cases. 



Sclerostomiasis produced by the larvae is of a much more serious 

 nature. Their most frequent location in this state is in the large arteries 

 where they bring about the formation of verminous aneurysms, usually 

 at the origin of the great mesenteric. Fragments of the clot within the 

 aneurysm may be carried by the blood to form emboli in the arterial 

 ramifications leading to the intestines, that portion of the intestine 

 supplied by an artery in which an embolus is lodged being deprived of its 

 normal supply of blood. As a result there is suspension of secretion and 

 peristaltic movements in this section, the walls of a portion of which 

 become dark and tumified with the presence of hemorrhagic infarct. 

 One or more portions of the intestine may be thus affected, the arrested 

 contents fermenting and producing an abundance of gas, while in the 

 healthy portions of the intestines there are abnormally energetic con- 

 tractions which cause a severe enteralgia and may lead to invagination, 

 displacement, and even rupture. The rupture may be of the paralyzed 

 intestine, or it may be of the stomach or diaphragm, brought about by 

 the accumulation of gas generated from the stagnated and fermenting 

 intestinal contents, the violent movements of the animal often con- 

 tributing toward this termination. 



Post-mortem Appearance. — The adult worms are fixed to the 

 mucosa, usually that of the cecum, where they nourish fi-om the blood of 

 their host and produce at their point of attachment a small dark prom- 

 inence. Immature worms may be found in submucous nodules of the 

 cecum, or of both the cecum and colon. These nodules vary in size from 

 that of a pinhead to that of a hazelnut and contain a small quantity of 

 pus or sero-purulent material in which the worm, if present, is rolled up. 

 The worms escape from the nodules by a central orifice to the lumen of 



