340 ENTOZOA. 



the larvae have been found in the muscular tissue. This has been 

 proved by direct experiment; for, by the feeding of dogs, cats, rab- 

 bits, rats, mice, pigs, and guinea-pigs with trichinous flesh, the larval 

 TrichinEe have attained their sexual maturity within less than forty- 

 eight hours after their introduction into the new bearer. In six days 

 the female parasites will contain perfectly- developed and free embryos 

 in their interior. Besides the above-named animals. Trichinae have 

 I believe, also, been obtained from the horse, ox, sheep, and other 

 ruminants. As soon as the embryos have attained their full size 

 within the uterus of the parent Trichina, they voluntarily pass out 

 at the vaginal opening, and commence wandering, as it were, on 



Fig. 74. — Embryos of Trichina in varioas stages of development. (Highly magnified.) — Leuckart. 



their own account. They do not, however, as some have supposed, 

 get into the blood-vessels to be transported by the circulation to 

 various parts of the body, but penetrate directly through the 

 walls of the intestinal canal, rapidly making their way through the 

 mucous, fibrous, and cellular tissues, in all directions, until they 

 arrive within the various voluntary muscles of the " host." In 

 this way, some of them reach the extremities and other parts far 

 removed from the spot whence they originally set out, and they sel- 

 dom stop in any non-muscular organ. In a cat which I dissected 

 many years ago, I found the lungs to contain tens of thousands of 

 microscopic Filari^, which I have since regarded as referable to this 

 genus; but Leuckart and others, by their experimental methods, have 



