DESCRIPTION OF THE PLATES. 113 



PLATE II. Fig. 1C. A portion of the same membrane, in which the 

 component flattened cells, with the centres, have 

 been rendered transparent, and are beginning to 

 separate, by the action of acetic acid. Five of 

 the glandular epithelia adhere to the membrane. 

 Fig. 17. A diagram of a lymphatic gland, showing the 

 intra-glandular network, and the transition from 

 the scale-like epithelia of the extra-glandular to 

 the nucleated cells of the intra-glandular lym- 

 phatics. 



Fig. 18. A portion of an intra-glandular lymphatic, showing 

 along one edge the thickness of the germinal 

 membrane, and upon it the thick layer of glan- 

 dular epithelia. 



THE STRUCTURE OF THE PLACENTA. 



Fig. 19. The extremity of a placental villus. 



a The external membrane of the villus, the lining 

 membrane of the vascular system of the mother. 



b The external cells of the villus, cells of the 



central portion of the placental decidua. 

 c c Germinal centres of the external cells. 



d The space between the maternal and fetal 

 portions of the villus. 



e The internal membrane of the villus, the ex- 

 ternal membrane of the chorion. 



/ The internal cells of the villus, the cells of the 

 chorion. 



g The loop of umbilical vessels. 



Fig. 20. This drawing illustrates the same structures as the 

 last, and has been introduced to show the large 

 space which occasionally intervenes between the 

 internal membrane and the external cells. It 

 would appear that into this space, the matter 

 separated from the maternal blood, by the ex- 



