446 THE PHYSIOLOGY OF REPRODUCTION 



of glandular detritus and the compact layer, which in turn form a 

 symplasina and undergo absorption. Thus the foetal structures reach 

 the spongy layer, in which the glandular cvls-de-sac have expanded 

 to form large cavities separated by partitions, the mesenteriform 



mj. 



tr 



FIG. 124. The angioplasmode of the dog at the thirtieth day of pregnancy. 

 (From Duval's "Le Placenta des Carnassiers," Journ. <b> VAnat. ct <!< lu 

 /'/>>/*., 1893.) 



ms, Mesoblast ; tr, trophoblast ; ac, ectodermic arcades ; ft, layer of 

 glandular detritus. 



lamelliv. Gradually the' roof of this layer is also absorbed by the 

 trophoblast, and the ectodermal arcades at the tips of the villi gain 

 a permanent attachment to the mesenteriform lamella-. At the same 

 time, by the further branching and penetration of the foetal meso- 

 derm in the angioplasmode, the tissue is broken up into a series of 

 labyrinthine lamellae, which consist of a network of maternal vessels 

 clothed on each side by syncytial trophoblast. The meshes of the 



