UROGENITAL SYSTEM 



819 



placental animals such as in rodents, there are two uteri formed each 

 with a separate opening into the vagina. (Fig. 461.) In the carnivores 

 and ruminants where the fusion is carried still farther back, forming in 

 reality two uteri with only one opening it is called a uterus bipartibus, 

 or where it is carried still farther forming two horns it is called uterus 

 bicornuus. For the uterus simplex the fusion is entirely complete, as in 

 all primates, the two Fallopian tubes alone remaining as evidence of its 

 bilateral formation. 



In the female the Wolffian duct and the mesonephros are largely 



Five varying uteri. A Monotreme; B, Marsupials; C, duplex uterus; D, 

 bicornuate uterus, and E, Simple uterus, ost.abd., abdominal opening (ostium) 

 into oviduct ; ovid., oviduct ; s.u.g., urogenital sinus ; ut, uterus ; vag., vagina ; 

 ves., urinary bladder. Such uteri as A and B open into the urogenital sinus, 

 while C, D, and E, open into the vagina. (After M. Weber.) 



lost in the adult, the mesonephros forming a small collection of tubules 

 near the anterior end of the ovary which is known as the parovarium. 

 In the male the Miillerian duct is also largely lost, the lower portion 

 sometimes persisting as a small blind tubule imbedded in the prostate 

 gland and known as the uterus masculinus. (Fig. 462.) 



Between the tubules in the testes there are small aggregates of cells 

 known as interstitial cells, which are glands of internal secretion. In 

 man their products, which pass into the blood, apparently cause the 

 assumption of the secondary male characters growth of hair on the 

 face, change of voice, etc. at the time of puberty. There would also 

 seem to be some analogous structure in the ovary governing the develop- 

 ment of female characteristics and controlling some of the features of 

 menstruation. 



There are also a number of accessory glands (Fig. 462) connected 

 with the genital ducts, usually better developed in the male than in the 

 female. The more prominent ones are: the seminal vesicles (present in 

 some rodents, bats, insectivores and in ungulates and primates) are a 

 pair of tubular or saccular glands opening into the vasa deferentia just 

 before these enter into the urogenital canal ; the prostate glands, (occur- 

 ing in all placental mammals with the exception of edentates and 

 whales) are connected with the urogenital canal, while farther along 



