52 WALTER HEAPS. 



cestrum in these animals ; or, in other words, the homology 

 between the pro-oestrum (so-called '^leat") of the lower 

 mammals and the menstruation of the Primates. 



The absence of Stage VII, the menstrual clot, is not to be 

 wondered at in a lai*ge bifid uterus ; the denudation of tissue 

 in sufficient quantity to form a clot would be a very severe 

 operation in such a comparatively large organ. 



The only other paper dealing with this subject, for the 

 bitch, with which I am acquainted (Johnstone, 1888), treats 

 of what the author calls the " corpuscular development " of 

 the mucosa of the bitch during the pro-oestrum, but I do not 

 gather the author has satisfactorily demonstrated the truth 

 of the view he advocates (see also Johnstone, 1895). 



Pouchet's description of the changes in the uterus of the 

 sow during pro-cestrum shows the existence of Stages II and 

 III (Wiltshire, 1883) ; he does not describe the breaking down 

 of vessels or the formation of lacunas, but his description of 

 the histology of the uterine discharge shows that it contains, 

 besides mucus, both blood and uterine epithelium. Stage IV, 

 therefore, is assuredly represented, and there can be little 

 doubt that Stages V and VI are also passed through, since 

 there must have been rupture of the uterine tissue in order 

 that pieces of it should be contained in the discharge. 



Ellenberger^s (1892) account of the changes which take 

 place during pro-cestrum in domestic mammals includes 

 Stages II and III ; he also does not describe Stages IV, V, 

 and VI, but he records the presence of both blood and epi- 

 thelial cells in the discharge, and these stages must therefore 

 have been passed through, although denudation is in all 

 probability very slight, Fleming (1878) adopts the view 

 that, among ruminants, the blood which finds its way to the 

 exterior exudes from the cotyledons; while EUenberger 

 describes pigmentation there, and states it is caused by 

 the blood left behind in that tissue after pro-cestrum has 

 occurred. 



Bonnet (1892) also describes Stages II and III in various 

 domestic mammals during pro-oestrum, but he also adds 



