726 MAMMALIA. 



supial Maramifer ; and even in the rest of the sexual parts obvious 

 relations may be traced between the rodent we are describing and 

 the ovo-viviparous quadrupeds. 



It is true that there are no longer two vaginae terminating in a 

 single cloacal cavity, but let the reader observe how nearly the va- 

 gina of the Rabbit (a, b) approximates the condition of a cloacal 

 chamber. Anteriorly it receives the contents of the bladder (d, m) ; 

 while the rectum (s) terminates by an anal orifice (r), so closely 

 conjoined with the aperture of the vulva, that the anatomist is 

 almost in doubt whether the external opening might not be de- 

 scribed as common both to the vagina and intestine. Advancing 

 from this lowest form of a placental uterine system, it is found 

 that the two uteri before their termination become united so as to 

 form a central portion common to both, called the body of the 

 uterus, through the intervention of which they communicate with the 



Fig. 334. 



vagina by a single passage named the os tinea ; still, however, 

 the cornua uteri, especially in those tribes that are most remark- 

 able for their fecundity, become during gestation far more capaci- 

 ous than the mesial portion of which they appear to be prolonga- 

 tions. It is, in fact, in the cornua that the numerous progenv of 

 such animals are lodged during the whole time of their retention 

 in the uterus ; and consequently such an arrangement is absolutely 

 requisite, as must be evident from simply inspecting the gravid 

 uterus of a Sow (fig. 335), where the cornua uteri (c, c,) are of 

 remarkable dimensions. 



