THE " SEXUAL SEASON " OF MAMMALS. ISl 



tissue contained in the clot apparently consists only of 

 desquamated epithelium. 



Retterer (1892) has given a more detailed account of what 

 happens during the pro- oestrum of the bitch. During period 

 A, of rest, Stage I, the mucosa of the uterine horns is firm, 

 pale, and of a thickness of "3 to '5 mm. ; but with the com- 

 mencement of pro-cestrum, period b, there is a well-marked 

 Stage, II, in which the mucosa grows rapidly to three or four 

 times its original thickness, and becomes soft and spongy. 

 Stage III is also well marked, and the mucosa becomes 

 injected with numerous vessels distended with blood. Then 

 period c occurs, and Stage IV is marked by the bi-eakiug down 

 of the vessels and extravasation of the blood iu the mucosa 

 tissue. Lacunas are formed. Stage V, which, during Stage 

 VI, rupture, and pour the contained blood into the uterine 

 cavity. 



So far the similarity of the progress of the pro-oestrum in 

 the bitch is practically identical with that of monkeys, but 

 there is no blood-clot formed, and Retterer's account renders 

 it doubtful whether any denudation, even of epithelium, takes 

 place. He himself thinks not. I have myself worked out 

 the history of the pro-oestrum of the bitch to some extent, 

 and have satisfied myself that Retterer's account is true in all 

 essential details. 



I have also failed to find any area of the uterine mucosa 

 which has been denuded of epithelium, and do not believe 

 that this process occurs to any extent; at the same time, 

 where lacunee rupture there must be loss of epithelium, though 

 I think denudation is confined to these spots. 



The pigmentation of the uterus, described by Altmann 

 (1878), is further evidence of the probability that much of 

 the extravasated blood is not discharged into the uterine 

 cavity, but is retained in the uterine tissue and absorbed from 

 thence. 



The homology of this process in the bitch with that already 

 described for monkeys is absolutely certain, and if nothing 

 more were known, would establish the identity of the pro- 



