VIVIPAROUS ANIMALS. 397 



the third kind, termed Uterus duplex, the horns, instead 

 of opening into a common cavity, enlarge each into a se- 

 parate uterus, opening by a distinct aperture into the va- 

 gina. This kind prevails in hares and rabbits. In the 

 American opossum and wombat, the uterus is double, with 

 an oviduct entering the summit of each cavity. Instead 

 of the uteri terminating separately in the vagina, as in the 

 hare, they unite to form a common neck or opening. 

 From each side of this neck a canal arises, and, after a se- 

 micircular course, terminates obliquely in the vagina. In 

 the kangaroo, the uterus is simple, with a trace of a di- 

 vision, by means of a longitudinal ridge on each side. The 

 oviducts terminate in the summit, one on each side of the 

 ridge. Near their termination on each side, a lateral canal 

 arises, which terminates in the vagina. The uterus, with 

 these lateral semicircular canals, has been termed Uterus 

 anfractuosus. 



The Vagina is a short dilatable canal, the walls of which 

 consist of cellular substance, supplied with bloodvessels, 

 and lined, internally, with a soft mucous covering. At its 

 origin it embraces the neck of the uterus, which usually 

 projects a little, and whose opening is denominated os tin- 

 ea, from a supposed resemblance to the mouth of a tench. 

 It is considered as terminating at the orifice of the urthera, 

 in the vulva, the common cavity opening externally, and 

 exhibiting, in the different species, very remarkable pecu- 

 liarities. 



The manner in which the uterine system is excited to 

 action, so as to produce impregnation, appears to be in- 

 volved in the deepest obscurity. Various conjectures have 

 been proposed, and hypotheses advanced, in the absence 

 of accurate observation or decisive experiment. That the 

 impregnating fluid is conveyed through the uterus and 

 oviducts to the ovarium, is rendered probable, by the 

 circumstance, that many of the eggs or germs of those 



