chap, iv.] ENDOTHELIUM. 29 



active state of division. They thus produce small 

 spherical lymphoid (amoeboid) cells, which ultimately 

 are absorbed by the lymphatics, and carried into the 

 blood system as white blood corpuscles. On the sur- 



Fig. 21. Part of Omentum of Cat, stained with Nitrate of Silver. 



f, Fenestrae or holes ; 6, trabeculae covered with endotheliura. Only the outlines 

 (silver-lines) of the endothelial cells are shown. 



face of the serous membranes, especially the diaphragm 

 (Fig. 20) and pleura, there exist minute openings, 

 stomata, leading from the serous cavity into a lym- 

 phatic vessel of the serous membrane. These stomata 

 are often lined by germinating cells. 



33. In the frog, germinating cells occur in great 

 abundance on the mesogastrium and the part of the 

 peritoneum which separates the peritoneal cavity 

 from the cisterna lymphatica magna. This part of 



