MAMMALIA. 299 



funnel-shaped opening of the corresponding oviduct. This con- 

 sists of a narrow convoluted Fallopian tube, which merges into a 

 cylindrical uterus, with thick muscular walls, which may be of 

 very large size in the pregnant female, and then exhibits a series 

 of oval swellings, in each of which an embryo is contained. The 

 two uteri open by separate apertures (ora uterorum) with rounded 

 projecting margins, into the vagina, a large tube which runs back 

 dorsal to the bladder, and becomes continuous with the urino- 

 genital canal (vestibule), a somewhat smaller but still wide tube, 

 which runs back from the bladder in the same relative position 

 as the narrow urinogenital canal of the male. The walls of this 

 tube are very vascular, and it ends in an elongated urinogenital 

 aperture (vulva). Imbedded in the ventral wall of the vestibule 

 is a small elongated body, the clitoris, supported by corpora cavernosa, 

 similar to, but very much smaller than, those of the penis, and 

 similarly situated. The clitoris ends in a soft, flattened glans 

 ditoridis. Small Cowper's glands open into the dorsal wall of the 

 vestibule. 



The ovary consists of Graafian follicles in various states of 

 development imbedded in a connective-tissue basis or stroma. 

 The mature follicles project from the surface of the ovary, and 

 each, when mature, is a fluid-containing vesicle, the wall of which 

 consists of a fibrous coat, internal to which are two or more layers 

 of columnar epithelial cells (membrana granulosa). The ovum is 

 placed on the outer side, and is surrounded by several layers of 

 these cells, with which it forms a mass, the discus proligerus, 

 that projects into the cavity of the follicle. The ripe ovum is 

 invested by a radiately striated membrane, the zona radiata, but 

 no distinct traces remain of the vitelline membrane present in the 

 young ovum. The vitellus contains hardly any food-yolk, and 

 within it is a large germinal vesicle with germinal spot. 



The ova burst from their follicles into the body-cavity, and are 

 taken up by the funnels of the Fallopian tubes. Fertilization is 

 effected in the upper part of these tubes, by fusion with sperms 

 previously ejected by the male into the female passages, the penis 

 being used as a copulatory organ. 



8. Muscular System (c/.p. 208). The muscles are very numerous 

 and arranged in a very complicated manner. The voluntary 

 muscles are from their appearance divided into red and white, the 

 darker colour of the former being due to their richer blood-supply. 



