THE FEMALE GENERATIVE ORGANS 549 



and others. 1 Excepting in the position of the placenta, the 

 new epithelium is completely regenerated by the end of the 

 sixth week after delivery. 



The placental area at the end of parturition is marked by 

 the presence of thrombosed vessels. It is raised above the 

 general surface of the uterine wall, and is irregular in shape. It 

 very soon diminishes in size, its diameter being not more than 

 two centimetres long at the end of the puerperal period, although 

 its former position may be detected as an area slightly stained 

 by blood pigment for several months after delivery. 



Williams states that in the last month of pregnancy some of 

 the sinuses at the placental area undergo thrombosis, but that 

 this process becomes much more marked after the completion 

 of labour, although many of the sinuses are simply compressed 

 by the contracting uterine muscles without ever becoming 

 thrombosed. 2 The thrombi are eventually converted into 

 ordinary connective tissue by a cellular proliferation from 

 the lining membrane of the vessels. While this change is in 

 progress the lining membrane presents a, folded appearance 

 somewhat resembling a typical developing corpus luteum. 

 This is especially well seen about the fourth week after parturi- 

 tion, but even up to the end of a year the convoluted appearance 

 is still sometimes discernible. 3 



The lumina of the arteries become reduced in size, but the 

 thickening of their walls, which takes place during pregnancy, is 

 an alteration of a more permanent character. This histological 

 change affords a means of discriminating between a virgin and 

 a parous uterus. 



The cervix uteri remains for some time after delivery as a 

 soft, flaccid structure with lacerated edges, but it gradually 

 undergoes involution, the lumen becoming narrower. The 

 vagina takes about the same time to recover as the uterus. 



1 Leusden, assuming the syncy tial tissue of the deciduum to be of maternal 

 origin, has suggested that it may assist in giving rise to the new epithelium 

 (" Ueber die Serotinalen Riesenzellen," &c., Zeitschr. f. Oeb. und Qynhk., 

 vol. xxxvi., 1897). 



- According to Longridge (see below in the text), thrombosis is of little 

 or no importance in assisting the hzemostasis of normal labour. 



3 Williams (Sir J.), "Changes in the Uterus," &c., Tran*. Obstct. Soc., 

 vol. xx., 1878. See also Helme, "Histological Observations," &c., Trans. 

 Roy. Soc. Edin., vol. xxxv., 1890. 



