C. Period of Degeneration. 



90 THE PHYSIOLOGY OF REPRODUCTION 



Heape has divided the cycle into the following four periods 

 and 'eigEF stages : — 



A. Period of Rest. Stage I. The Resting Stage. 



„ . , „ „ , r, ,' II. The Growth of Stroma. 



B. Period of Growth. ^^^ III. The Increase of Vessels. 



f„ IV. The Breaking Down of 

 Vessels. 

 V. The Formation of Lacunae. 

 VI. The Rupture of Lacunse. 

 VII. The Formation of the 

 Menstrual Clot. 

 D. Period of Recuperation. „ VIII. The Recuperation Stage. 



Heape's account may now be briefly summarised. 



I. The Resting Stage. — ^The epitheUal layer of the uterine 

 mucosa consists of a single row of cubical or columnar cells. 

 The outer border is clearly defined, but on the inner side the 

 protoplasm of the epithehum is continuous with that of the 

 sub-epithelial mucosa or stroma tissue. The surface epithehum 

 is continuous with that of the glands, but the latter rest on a 

 basement-membrane which separates them from the inter- 

 glandular stroma. The stroma contains round nuclei embedded 

 in a network of protoplasm, with fine, dehcate processes in 

 which granules may be seen. In Semnopithecus fibrils running 

 fan-wise were observed in the deeper parts of the stroma, but 

 these were not seen in Macacus. Multiplication of cells was not 

 noticed at this stage, either in the epithelium or in the stroma. 

 The vessels in the mucosa are small. A few arteries occur in 

 the deeper portion, but only thin-waUed capillaries in the more 

 superficial part ; the latter, however, are fairly numerous. 



II. The Growth of Stroma. — The nuclei of the more superficial 

 part of the stroma undergo a great increase, the division being 

 amitotic in character, at least so far as could be seen. As a 

 consequence the mucosa in its upper third becomes considerably 

 swelled (hyperplasia), but in the deeper portion there is no 

 change in the tissue. Owing to the efiects of pressure the 

 nuclei become elongated or fusiform. Division occurs either 

 by fragmentation or by the nucleus simply sphtting into two. 

 The growth in the upper part of the stroma is associated with 

 an increase in the size of the blood-vessels in the deeper part. 



