314 ANIMAL PARASITES. 



for several days in water, and that it may be dried up and 

 again brought to life by water. Accordingly there would cer- 

 tainly be a possibility of infection by direct immigration from 

 without ; but it is just as possible that the brood may only be 

 set free after a passive immigration into the stomach of a human 

 individual, and then bore onwards into the blood-vessels, and 

 reach its future habitation through these. 



With regard to the developmental history of the other species, 

 we are still equally in the dark. The little that we know 

 positively at present may be sumrSed up as follows. 



1. The Oxyurides (thread- worms) are apparently capable of an 

 active migration, even when mature and sexually developed ; they 

 prefer performing these migrations at night. Any one who 

 inquires in his practice will hear his patients complain that 

 little worms creep out of them by the anus, causing a violent 

 itching. Thus a shoemaker came to me for advice, as the 

 Oxyurides disturbed him at night. As soon as he went 

 to bed and got warm, the Oxyurides began to march out of his 

 anus, with violent itching, and wander about in the anal folds, 

 and even, in his opinion, attempted to free themselves by biting. 

 Once, when he did not know what to do with himself, he 

 wakened his wife and begged her to see whether she could not 

 discover what it was that troubled him so much. By means of 

 a light the woman found the little white worms, and picked 

 them off, and since then, whenever he was again troubled, she 

 always did him the same service. Moreover, that Oxyurides 

 creep from the anus into the vagina, in little girls, is a fact 

 known to the oldest surgeons. It may also be taken for 

 granted that the worms found were females, and indeed preg- 

 nant females, as the males are far too small to be detected, 

 although we may also suppose that the males may sometimes 

 emigrate. However, the emigration of a single pregnant female 

 is sufficient to explain the infection of whole families with 

 Oxyurides. From what has just been said, the following hypo- 

 thesis may be deduced as to the active migration of mature 

 females of Oxyuris from the intestine of one human being 

 to that of another. The sleeping of a married couple, one of 

 whom is affected with Oxyurides, in the same bed, which is 

 especially the case amongst the poor who only possess one bed, 

 the sleeping of these parents with their children, or of several 

 children together, one of which is troubled with Oxyurides } is 



