90 THE PHYSIOLOGY OF REPRODUCTION 



found no evidence of destruction of the uterine mucosa, not even 

 of the epithelium, but the uterus was distinctly congested, and there 

 was an escape of blood into the cavity. It should be noted, however, 

 that Sutton's investigation was upon monkeys in this country, 

 whereas Heape's observations relate to Indian animals, and that 

 in Pocock's experience,^ menstruation does not, as a rule, occur in 

 Maeacus rhesus in the Zoological Gardens. But it would appear also 

 from this aythor's observations that the severity of the menstrual 

 process in monkeys may vary within as wide limits as it is said to 

 do in the human female. 



The changes which occur throughout the menstrual cycle in 

 Gercocebus cynomolgus have been studied in some detail by van 

 Herwerden,^ who begins by classifying the material in two groups. 

 In group A are included those animals in which, at the time of 

 killing, the uterus was relatively small and menstruation was 

 correspondingly slight. In group B are placed those monkeys 

 which, on being killed, showed comparatively large well-developed 

 uteri, and in which the menstrual process was characterised by 

 some degree of severity. Van Herwerden is of opinion that the 

 individuals included in the first category were animals killed during 

 the non-breeding season, while those belonging to group B were 

 specimens killed at the breeding season, when the generative organs 

 were in a state of greater activity. 



The complete menstrual cycle in Gercocebus is divided into the 

 following periods and stages : — 



I. Inter-menstrual period. 



II. Pre-menstrual period - ( I ^^9"^^?^ of superficial stroma elements. 



^ \% Slignt swelling of mucosa. 



Increasing hyperaemia. 

 Rupture of capillaries. 



I 3. Formation of lacunae, 



J 4. 



III. Menstrual period - -( ^- "'^^^elemTntr °^ ^P'*^®^'""" ^'"'^ '*™'"^ 



Eupture of lacunae and tearing off of 



I'- 



degenerate tissue. 

 Beginning of regeneration. 



IV. Post-menstrual period. 



. It will be seen from this scheme of classification that the 

 changes recorded by van Herwerden as occurring in the menstrual 

 cycle of Gercocebus are very similar to those described by Heape in 

 Semnopithecus and Maeacus. Both authors agree in stating that the 

 superficial portion of the mucosa is denuded during the destruction 

 period, differing thus from Bland Sutton and those writers on human 

 menstruation (referred to above) who maintain that the denudation 



1 Pocock, " Notes upon Menstruation etc.," Proa. Zool. Soc, 1906. 



2 Van Herwerden, loc. cit. 



