230 THE UROGENITAL SYSTEM 



dividual possesses testicles, but the external genitals (by retarded development) 

 and secondary sexual characters are like those of the female. In feminine her- 

 maphroditism ovaries are present, but the other sexual characters (e. g., abnor- 

 mally developed cUtoris) are male. The cause of hermaphroditism is unknown. 



THE UTERUS DURING MENSTRUATION AND PREGNANCY: PLACENTA 

 AND DECIDUAL MEMBRANES 



Two sets of important changes take place normally in the wall of the uterus. 

 One of these is periodic between puberty and the fortieth to forty-fifth year 

 and is the cause of menstruation (monthly flow) . These periodic changes may also 

 be regarded as preparatory to the second set of changes which take place if preg- 

 nancy occurs and give rise to the decidual membranes and placenta. 



Menstruation. — The periodic changes which accompany the phenomenon 

 of menstruation form a cycle which occupies twenty-eight days. This period is 

 divided into: (1) a phase of uterine congestion — six or seven days; (2) a phase of 

 hemorrhage and epithelial desquamation — three to five days; (3) a phase of 

 regeneration of the uterine mucosa — ^four to six days; (4) finally, an interval of 

 rest or slight regeneration — twelve to sixteen days. 



During the first phase, the uterine mucosa is thickened to two or three times 

 its normal condition, both because of vascular congestion and on accoimt of the 

 actual increase of reticular tissue. The uterine glands become longer and their 

 deeper portions especially are dilated and more convoluted because they are 

 filled with secretion. From the enlarged veins and capillaries blood escapes into 

 the reticular tissue and forms subepithelial masses. At the end of this stage the 

 uterine mucosa shows a deep spongy layer and a superficial compact layer, these 

 corresponding to similar layers in the decidual membranes of pregnancy. 



During the second phase, that of menstruation proper, blood escapes into 

 the uterine cavity between the epithelial cells of the mucosa and there is an active 

 discharge of secretion from the uterine glands: The surface epitheKum and a 

 portion of the underlying tissue may or may not be desquamated. In some 

 normal cases the surface epithelium and most of the compact layer may be ex- 

 pelled, aided by painful contractions of the uterus. 



In the third stage, the mucosa becomes thin, with straight, narrow glands, 

 between which are fusiform, closely packed stroma cells. Any surface epithelium 

 which has been desquamated is regenerated from the epithelium of the glands 

 and gradually the mucosa returns to a resting condition during which, however, 

 there is a slow process of cell proliferation. 



