CHANGES IN THE UTERUS IN PREGNANCY. 565 



but which is again rapidly restored after the catamenial period has 

 passed (p. 176, E.) 



In pregnancy, changes of a very different character occur ; the 

 increased bulk of the organ being, however, the subject of main 

 interest here. The principal changes occur in the muscular struc- 

 ture of the uterus; and these have already, been described on page 

 388. But the mucous membrane also undergoes manifold changes ; 

 it being also first affected. As early as the second week in preg- 

 nancy it becomes 2 to 3 lines thick, is softer, redder, has more pro- 

 minent plica, and is more distinct from the muscular coat. The 

 uterine glands become 2 to 3 lines long ; and a new formation of 

 areolar tissue has taken place in the coriurn. These peculiari- 

 ties become more marked as time advances; and the greater part 

 of the hypertrophied mucous membrane is transformed into the 

 decidua vera, while that corresponding to the attachment of the 

 ovum is converted into the placenta uterina, and a growth from the 

 border of this produces the reflexa around the ovum. No epithe- 

 lium exists on the decidua after the first month. The mucous mem- 

 brane of the cervix takes no part in this formation, and retains its 

 epithelium (without cilia), during the whole period of pregnancy. 



The serous coat of the uterus also increases in thickness during 

 pregnancy, but less than the mucous. The smooth muscular fibres 

 also, .and probably the striated, increase in the round ligaments. 

 The bloodvessels and lymphatics also increase in length and calibre, 

 and the nerves appear to become thickened (though it is doubtful 

 whether- any new fibres are produced in them), and may be traced 

 further into the organ than at other times. 



The return of the uterus after parturition to a state similar to, 

 but not precisely identical with, its condition previously to that 

 state, is effected (1,) by an atrophy of the muscular structure, so 

 that in three weeks after parturition the fibres are as short as in the 

 virgin uterus (p. 389); and (2,) by the complete removal after par- 

 turition of the placenta and decidua, so that the membrane has to 

 'be formed anew. 



4. The ovaries consist of two coats, the peritoneal and the fibrous 

 (tunica albuginea), and the stroma. The last is a grayish-red, 

 tolerably firm substance, composed of embryonic areolar tissue, 

 which contains the ovisacs, or Graafian follicles, and the vessels. 

 The ovisacs are entirely closed round cavities J to 3 lines in dia- 

 meter, and imbedded in the more peripheral parts of the stroma. 



