108 THE PHYSIOLOGY OF REPRODUCTION 



along with the red corpuscles, but there is no evidence of the 

 existence of wandering cells apart from those which are derived 

 apparently from the broken-down vessels. The blood tends to 

 collect below the epithelium. Bleeding into the uterine cavity 

 may occur, but is not invariable. A few epithelial cells are 

 sometimes torn off (presumably in places where blood is poured 

 out into the cavity), but destruction even to this extent does not 

 necessarily take place. Denudation of the stroma has never 

 been observed. It would seem that the severity of the pro- 

 cestrous process tends to diminish with each successive dioestrous 

 cycle in the breeding season, and that sometimes in a late 

 procestrum the period of destruction is never reached, the 

 congested vessels subsiding without undergoing rupture. Bleed- 

 ing, when it does occur, appears to be more frequent in the 

 cotyledonary papillae than between them, and is commoner in 

 the large papillae than in the smaller ones. 



Kazzander 1 appears to have been the first to detect ex- 

 tra vasated blood in the sheep's mucosa. Subsequently Bonnet 2 

 has noted uterine bleeding in various Ruminants, as well as in the 

 mare and sow, and Kolster 3 has made similar observations 

 (cf. also Emrys-Roberts, see p. 47). Ewart also has described 

 procestrous extravasation and the presence of haBmatoidin 

 crystals in the uterus of the mare. Glandular activity during 

 heat was also noted. 4 



(4) Period of recuperation. The sheep's prooestrum may be 

 said to end with the period of destruction, the entire process 

 probably lasting for not longer than one or two days, its exact 

 duration depending upon its severity. (Estrus itself, which 

 occurs during the beginning of the period of recuperation, some- 

 times occupies only a few hours. 



In those places where bleeding into the cavity took place in 

 the preceding period the epithelium is renewed, apparently 



1 Kazzander, " Uber die Pigmentation der Uterinschleimhaut des Schafes," 

 Arch.f. Mikr. Anat., vol. xxxvi., 1890. 



2 Bonnet, article in Ellenberger's Vergleichende Physiologic des Haussduge- 

 thicre, vol. ii., Berlin, 1892. Cf. also Ellenberger's article in same volume. 



3 Kolster, " Weitere Beitriige zur Kenntniss der Embryotrophe bei Indeci- 

 dunten," Anat. Hefte, vol. xx., 1902. 



4 Ewart, " The Development of the Horse," Quar. Jour. Micr. Science, 

 (not yet published). 



