48 WALTER HEAPE. 



domesticated animals, mares, cows, sheep, and rabbits do not 

 always experience a loss of blood ; further, individual animals 

 of these species sometimes experience a much more profuse 

 flow than at other times, or they may experience a profuse 

 flow only rarely or not at all. 



The Internal Phenomena of Pro-oestrum. — It will 

 be convenient first to abstract the account I have given else- 

 where (Heape, 1894) of the changes which take place in the 

 uterus of the monkey during pro- oestrum, and then to com- 

 pare these changes with those which occur at that time in the 

 human female on the one hand, and in the lower animals on 

 the other. 



A. Period of Eest. — Stage I. The resting stage. This is 

 the period before pro-oestrum occurs, and at that time the 

 uterine mucosa is a shallow bed, opaque, white, and anaemic. 



B. Period of Growth. — Stage II. The growth of stroma. 

 It is now that pro-oestrum first becomes apparent ; the uterine 

 stroma thickens, hypertrophy takes place, and it becomes 

 semi-transparent, soft, and flabby. 



Stage III. The increase of vessels. The growth of the 

 stroma tissue is rapidly followed by an increase in the number 

 and size of the vessels of the stroma, the whole becomes 

 richly supplied with blood, and the surface is flushed and 

 highly vascular. This process goes on until the whole of 

 the uterine stroma becomes tense and brilliantly injected 

 with blood. 



c. Period of Degeneration. — Stage 4. The breaking 

 down of vessels. The walls of the superficial vessels now 

 break down, and the blood contained therein is extravasated 

 throughout the superficial portion of the mucosa. 



Stage V. The formation of lacunae. The extravasated 

 blood becomes gradually collected in lacuna, which at first 

 lie within the stroma, but gradually become enlarged and 

 project as rounded hillocks, bounded superficially by the 

 uterine epithelium, into the cavity of the uterus. 



Stage VI. The rupture of lacunae. The superficial mucosa 

 cells, isolated or in patches, now begin to degenerate ; they 



