296 PROFESSOR J. COSSAR EWART. 



rudiments of glands, but by the third month a number of deep furrows extend along 

 the horns and along the greater part of the body of the uterus. By the end of the 

 first year the uterine mucous membrane, from a short distance within the cervix up 

 to the ends of the horns, is folded longitudinally to form narrow nearly parallel 

 ridges separated by deep furrows. Eventually these ridges are cut transversely into 

 numerous tongue-shaped processes (figs. 14 and 2l). The condition of the uterine 

 mucous membrane at the end of the third week is indicated in figs. 25 and 26. 

 With the exception of the cervix the uterus is lined by a layer of columnar 

 epithelium beneath which is a somewhat dense layer of connective tissue traversed 

 by numerous capillaries (fig. 24). At a deeper level the connective tissue of the 

 uterine wall forms an irregular network the meshes of which are traversed by blood- 

 vessels of various sizes, and by the numerous uterine glands (fig. 26). 



Before prooestrum sets in — i.e. during the period of rest (anoestrum) — the uterine 

 mucosa is of a pale colour and coated with a thin layer of mucus ; but as prooestrum 

 advances it becomes more and more congested, with the result that the glands become 

 more active. When the oestrous phase is reached the tongue-like processes making 

 up the uterine ridges (figs. 14 and 21) are red and swollen ; this is partly due to con- 

 gestion of the capillaries, and partly to the engorged condition of the glands. An 

 indication of the condition of the mucous membrane during oestrus will be gained 

 from figs. 23 and 24, which represent sections of a uterine ridge about 24 hours 

 after oestrus set in. The sections, though affording no evidence of the escape of blood 

 into the cavity of the uterus during prooestrum, show at places extravasated blood 

 in the connective tissue and in the lumen of the glands. It will be noticed that 

 amongst the extravasated blood corpuscles bodies resembling hsematoidin crystals 

 (fig. 24) are fairly common ; there is, however, an absence of pigment such as usually 

 occurs in sheep. # 



Martin states that the mucous membrane of the uterus from which his 35-mm. 

 blastocyst was obtained was swollen and spotted. There was no spotting or evidence 

 of congestion in the uterine horn which contained my 21 -days embryo; in fact, at 

 the end of the third week, as during anoestrum, there is neither marked congestion 

 nor evidence of unusual activity of the uterine glands nor yet of destruction of the 

 uterine epithelium. In the absence of signs of unusual activity in the uterine mucous 

 membrane during the earlier weeks of gestation the mare evidently differs from the 

 sheep and pig, in which, in addition to an increase of the interglandular tissue, there 

 is considerable degeneration of the lining epithelium. An indication of the difference 

 between the uterine mucosa at the end of the third week and during oestrus will be 

 gained from figs. 23 to 26 ; in figs. 25 and 26 the mucous membrane of the uterine 

 horn containing the 21 -days embryo is represented, in figs. 23 and 24 the mucous 

 membrane at the end of the first day of oestrus. 



Notwithstanding the absence of marked congestion of the mucosa at the end of 



* Marshall, "The (Estrus Cycle in the Sheep," Phil. Trans., Ser. B, vol. cxcvi, 1903. 



