DEVELOPMENT OF OXYURIS. 315 



sufficient to infect whole families with these worms. For if only 

 a single female which emigrated at night, has wandered into the 

 intestine of one of the bedfellows who has hitherto been free 

 from Oxyurides, the perpetual infection is established in con- 

 sequence of the abundant reproduction of this parasite. In this 

 process we have an analogue to the immigration of certain 

 Cercari&j which, swimming freely in the water, creep directly 

 into the rectum of the frog. What becomes of the young 

 Oxyurides which pass out with the fceces I know not. After 

 keeping the eggs for six months in water I could discover 

 neither mature embryos, nor a distinct segmentation. I usually 

 saw in the interior of the egg, at a considerable distance apart, 

 two rather large hyaline globules, and round about finely 

 granular detritus, and I do not know whether in this case there 

 was a decomposition of the vitellus in accordance with the laws 

 of putrefaction, or with those of development. The former 

 appears to me most probable, and then perhaps the development 

 of the embryos would only be able to take place in the animal 

 body with the aid of animal warmth. 



2. The mode in which we become infected with Trichocephali 

 may be the same as that by which, as we have already shown, 

 the infection with Tania solium is effected. That pigs contain 

 Trichina exactly like those of man, is evident from the ob- 

 servations of Leidy, in Philadelphia, described further on ; he has 

 therefore given the name of Trichina affinis to the encysted 

 round- worm discovered by him. We shall hereafter attempt to 

 prove the probability of a relationship between Trichina spiralis 

 and Trichocephalus dispar. It is therefore sufficient that we 

 should eat raw " trichinous" pork, to bring Trichocephali 

 upon us, and all that is necessary is to refer to the mode of 

 infection with T&nia solium by the use of swine's flesh already 

 indicated. Unfortunately the experiment of administration to 

 dogs has not succeeded (vide infra), and it is also to be regretted 

 that at present we possess no statistics as to the occurrence and 

 diffusion of the Trichocephali with reference to the trades and 

 occupations of their human hosts. After preserving the eggs of 

 Trichocephalus for six months in water, no embryos appeared, but 

 only numerous, clear, but pretty regularly arranged globules, 

 in the place of the vitellus, which certainly presented the 

 same appearance as the processes in the segmentation of the 

 vitellus. 



