232 PARASITES OF THE DOMESTIC ANIMALS 



by which the condition can be recognized. Where there is a heavy in- 

 festation they cause injury by their irritation to the intestinal mucosa. 

 In such cases they may become massed and constitute an obstruction 

 to the intestinal lumen sufficient to cause stasis of the contents and de- 

 generative changes in the intestinal walls. 



The ascarids are active worms, and have a tendency to wander to 

 unusual locations; one or two may find lodgment in accessory organs of 

 the intestines by way of their ducts and, by the consequent continuous 

 irritation, bring about results of a serious nature. Verminous fistulae 

 may be thus established, or there may be abscess formation with dis- 

 charge of pus into the peritoneal cavity, followed by peritonitis. In 

 dogs and cats especially, the worms when numerous often pass to the 

 stomach in considerable numbers, setting up more or less gastric dis- 

 turbance and consequent vomiting, the expelled material generally 

 containing from one to several worms. 



Certain foreign investigators, having demonstrated the presence of 

 blood in ascarids, have concluded from this that these worms are blood 

 suckers. Hall, in an article upon the parasites of the dog in Michigan 

 (Journal of the American Veterinary Medical Association, June, 1917), 

 states that an ascarid which he collected from the feces of a dog showed 

 a pronounced red color in the intestine, evidently due to blood. As 

 post-mortem examination of the dog the same day revealed a severe 

 hemorrhagic enteritis, he concludes that this was evidently the explana- 

 tion for the blood in the intestine of the ascarid. The conditions found 

 in this case suggest the possibility of similar conditions in cases regarded 

 as evidence that these worms are blood suckers, — a conclusion that cer- 

 tainly has no support in the stnicture of the ascarid's mouth. 



There seeins reason to doubt that ascarids feed upon epithelial cells, 

 as stated by some authors. Their simple intestinal tube is restrictively 

 modified to the primary function of absorption of nutriment already 

 made in a certain state of solution by the digestive juices of the host, 

 and it is unlikely that such digestive powers as are retained by the 

 parasites would be adapted to a diet of epithelial cells. In view of the 

 fact that free epithelial cells and their debris are contained in the alimen- 

 tary contents of the host, it follows that such material would be in- 

 gested along with the alimentary matter by the worms and would be 

 found in their intestinal contents. 



Aside from the mechanical injury caused by the ascarids, there are 

 to be considered the effects of toxic products elaborated by their bodies. 

 These may be practically nil or considerable according to the character 

 and degree of the infestation. The loss of condition in heavy invasions 

 can probably be attributed to the systemic effect of these poisons com- 

 bined with that of the catarrhal enteritis. It seems reasonable to con- 

 clude that the deprivation of nutriment, which has been appropriated 



