BY N. A. COBB. 169 



It has been found that both sexes of this parasite inhabit the 

 human intestine in about equal numbers.* They reach there their 

 full size, feeding upon the contents of the intestine, and the females 

 produce and lay eggs which may be found in almost every particle 

 of the excrement of persons suffering from an attack of Oxyuris. 

 The adult females have a tendency to wander to and outside of 

 the anus, especially at evening, probably for the purpose of laying 

 their eggs. It is these females which cause the itching sensation 

 peculiar to attacks of " piaworms." If the offending worms be 

 artificially removed they are invariably found to be adult females 

 having their sexual organs distended with eggs which they Vjegin 

 to deposit immediately on exposure to the outer aii-. 



It was when we came to the fate of the eggs that uncertainty 

 prevailed. It was held on the one hand that the eggs hatched and 

 developed only in the large intestine, and the entire cycle of life thus 

 completed in the birth-place. Holding this view, Vix contended 

 that a person once infected with x y u r i s might remain so 

 indefinitely. On the other hand, and as we shall see with better 

 reason, it was contended that the eggs hatched normally only on 

 being introduced into the human stomach. 



Those holding the first view based their belief on the occur- 

 rence side by side in the same intestine of all the stages in the 

 development — eggs, larvae, and adults. At first sight this seems 

 plausible enough, but further thought shows that the same facts 

 support the second view to an extent almost if not quite equal. 



* Leuckart and many others state that the females ai-e more abundant than 

 the males, and Leuckart gives as the result of his investigations tlae ratio 9:1. 

 Devalue however believes the males to be as abundant as the females and I 

 will add a case supporting his view. I took the entire mass passed from 

 thoroughly purging a case of Oxyuris and poured it into hot corrosive 

 sublimate solution, shook immediately and violently, and then examined 

 the whole precipitate most carefully under a powerful magnifying glass, 

 with the best illumination. Being practised in seax'ching for much smaller 

 free-living Nematodes, treated in a similar manner, I am confident that 

 none or almost none escaped the scrutiny. The result was 49 males and 

 52 females. 



