STRONGYLOIDES 



279 



even large numbers of pinworms, since they do not suck blood 

 and seldom cause intestinal lesions, yet they sometimes produce 

 reflex nervous symptoms, probably by secretion of toxins, and 

 they may interfere with the normal action of the bowels. As 



Fig. 112. Early development of pinworm, Oxyuris vermicularis. A, newly laid 

 egg containing tadpole-like larva; B, egg 12 hrs. later with nematode-lilce larva; 

 C, egg with fully developed embryo ; D, newly hatched embryo. X 500. (4 and 

 B after Braun; C and D after Leuckart.) 



remarked elsewhere pinworms are believed to be sometimes, 

 and perhaps frequently, the original cause of lesions in the ap- 

 pendix which culminate in appendicitis. The intense itching 

 which they produce by creeping in the vicinity of the anus is 

 usually the most disagreeable effect of their presence. 



On account of their situation in the lower part of the intestine, 

 treatment for pinworms should be by drugs which are not rapidly 

 absorbed from the intestine but are relatively insoluble. Thy- 

 mol, male fern and, best of all, oil of chenopodium are effective 

 remedies. 



Strongyloides. — Another parasite of the intestine which is of 

 wide distribution and locally very common is Strongyloides ster- 

 coralis, a very small worm about one-tenth of an inch in length 

 which bores deep into the mucous membrane of the intestine. The 

 female strongyloid (Figs. 106 and 113A), which is the only 

 sex known, can be recognized by its small size, and microscopi- 

 cally by the chain of six or eight eggs, lying near the middle of 



