THE GRAVID UTERUS 423 



consist in increased vascularity, hypertrophy of the elementary 

 tissues of the mucosa, epithelial desquamation, and rupture of the 

 blood vessels, with consequent hemorrhages. These changes are 

 followed by a process of regression and later of regeneration, by 

 which the uterine mucosa rapidly returns to its former condition. 



The first or hypertrophic stage involves the epithelium, whose 

 cells are elongated, and the tunica propria, in which many of the 

 connective tissue cells undergo multiplication and enlargement. 

 Thus the mucous membrane becomes greatly thickened ; its glands, 

 also, are increased in both length and breadth, becoming at the 

 same time even more tortuous than before. The glandular hyper- 

 trophy involves both the uterine and the cervical glands ; the secre- 

 tion of the latter is much increased. 



At the same time, the blood vessels become widely dilated, 

 especially those near the surface, and broad thin-walled sinuses 

 are formed beneath the epithelium. Finally these vessels rupture 

 and hemorrhages occur into the substance of the mucosa as well 

 as into the cavity of the organ ; desquamation and disintegration 

 of the superficial portions of the mucosa result. The menses which 

 are thus formed contain blood, epithelium, connective tissue cells, 

 and many leucocytes, which wander out from the blood vessels of 

 the mucosa in large numbers. The greatly thickened and hemor- 

 rhagic mucosa is known as the decidua menstrualis. 



Regression and regeneration follow rapidly upon one another, 

 the mucosa gradually regaining its former condition. During this 

 process fat droplets appear in. many of the connective tissue cells. 

 The epithelium is rapidly regenerated, the new cells arising from 

 the epithelial remnants at the mouths of the uterine glands. In 

 the course of a few days the mucosa regains its former quiescent 

 condition. 



THE GKAYID UTERUS 



In the event of conception the uterine changes are even more 

 pronounced than during menstruation. These alterations include 

 the same processes of hypertrophy and thickening as occur in the 

 decidua menstrualis ; they involve the musculature as well as the 

 mucosa but are not followed by regressive changes, hemorrhage, 

 desquamation, etc. until parturition occurs. 



The muscular wall undergoes an enormous increase both in 

 the number and size of its fibres. The relatively short (30 to 60 /A) 

 smooth muscle fibres of the uterine wall gradually increase in 

 size to as much as eleven times their former length and two to 



