REPRODUCTION^ ^ 511 



bryo is retained and nourished. The lowest part of the cervix 

 reaches into the vagina and communicates with it by a transverse 

 aperture, the os uteri. During gestation or pregnancy the fetus 

 develops in the body of the womb, which becomes greatly enlarged 

 and rises high into the abdomen: the virgin womb lies mainly 

 below the level of the bones of the pelvis. 



The chief bulk of the non-gravid uterus consists of a coat of 

 plain muscular tissue, arranged in a thin outer longitudinal layer, 



FIG. 151. The uterus, in section, with the right Fallopian tube and ovary, as 

 seen from behind, about f the natural size, u, upper part of uterus; c, cervix; 

 v, upper part of vagina; od, Fallopian tube; fi, its nmbriated extremity; o, ovary; 

 po, parovarium. 



and an inner, thicker, consisting of oblique and circular fibers. 

 Between the layers is an extensive vascular network, with many 

 dilated veins or venous sinuses. The muscular coat is lined in- 

 ternally by a ciliated mucous membrane, and is covered externally 

 by the peritoneum, bands of which project from each side of it 

 as the broad ligaments (II, Fig. 151). The outer layer of the mucous 

 membrane presents a very well developed muscularis mucosce, 

 much thicker than the corresponding layer in the gastric or intes- 

 tinal mucous membranes and much less sharply marked off from 

 the true muscular coat outside it. The main thickness of the 

 mucous membrane consists of closely set, simple or slightly 

 branched, tubular glands; between these is a close blood-vascular 

 and lymphatic network. The glands open on the interior of the 

 womb; they and the mucous membrane between their mouths are 

 lined by a single layer of columnar ciliated cells, with some gob- 



