GESTATION. I2i 



depressions, lying more or less closely together throughout the whole of 

 the uterine mucous membrane of the Mare, their cavity being lined by a 

 layer of tessellated epithelium, and a very fine capillary network surround- 

 ing each. In the Cow, these crypts are assembled on the surface of the 

 projections designated cotyledons, of which they constitute nearly the 

 entire mass during pregnancy. In the Bitch, they are only developed 

 where the ovule is fixed, forming then a glandular layer occupying the 

 contour of the uterine cornu. 



The utricular glands do not open directly into the crypts^ nor is their 

 secretion poured into them, but on a definite surface of the mucous mem- 

 brane between the crypts, the size and areas of which correspond, of 

 course, to the size and arrangement of the foetal tufts. 



Between the foetal and maternal placentae, there is always a layer of 



Vertical Section through a Portion of the Uterine Cotyledon of 

 AN Early Stage of Pregnancy. 



Cow in 



a, Serous Membrane; 3, Section of Longitudinal Muscular Layer; c. External, andfi, Internal 

 Layers of the Circular Muscle ; d, Submucosa, with vessels ; e, Adenoid Tissue of the Cotyle- 

 don ; f. New Tissue of the Placenta Uterina ; g, Section of the Mucous Layer of the Cotyle- 

 don, with the Interspaces into which the Foetal Cotyledons are inserted ; h k, Utricular Glands 

 passing under the Side of the Cotyledon; i i, Large Cotyledonal Vessels; k, Uterina Mucosa; 

 //, Epithelial Layer of the Cotyledon. 



epithelial cells of varying thickness, which represents the membrana 

 decidua or serotlna of woman. If not during parturition, at least after- 

 wards, all placental mammals are " deciduate," more or less. With the 

 Cow and Sheep, for example, large quantities of cells, possessing the 

 character of epithelial cells of the pits and crypts of the maternal cotyle- 

 dons, have been found, mingled with the villi of shed foetal cotyledons, 

 in the fluid extruded during and after parturition : showing that a 

 portion of the maternal structure is carried away at this time. The 

 crypts possess structural characters of secreting organs ; and, indeed, 

 we cannot but look -upon the maternal placenta and the remarkably modi- 

 fied mucous lining of the uterus as a great secreting organ. 



In addition to the mucous membrane, the outer or serous membrane is 



