XV 111 EXPLANATION OF THE PLATES. 



THE STRUCTURE OF THE LYilPHATIO GLANDS. 

 Plate V. page 412. 



Fig. 15. A portion of the germinal membrane of the human intra- 

 glandular lymphatics, with its germinal spots or nutritive 

 centres difrused over it. 



Fig. 16. A portion of the same membrane, in which the component 

 flattened cells, with the centres, have been rendered trans- 

 parent, and are beginning to sejiarate, by the action of acetic 

 acid. Five of the glandular epithelia adhere to the mem- 

 l>rane. 



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 lymphatics. 



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 glandular epithelia. 



THE STRUCTURE OF THE PLACENTA.— Plates V. VL 



Plate V. page 412. 



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. 

 h. 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 foetal portions of the 



villus. 

 c. The internal membrane of the villus, the external membrane 



of the chorion. 

 /. The internal cells of the \dllus, the cells of the chorion. 

 (j. The loop of umbilical vessels. 

 Fig. 20. This drawing ilhistrates 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 external cells of 

 the villus, is cast before being absorbed through the internal 

 membrane, by the internal cells. This space, therefore, is 

 the cavity of a secreting follicle, the external cells being the 

 secreting epithelia, and the maternal blood-vessel system the 

 capillaries of suj^ply. This maternal portion of the villus, 

 and its cavity, correspond to the glandular cotyledons of the 

 ruminants, and the matter thrown into the cavity to the 

 milky secretion of these organs. 



