HANDBOOK OF PHYSIOLOGY. 



The presence of enclothelium in any locality may be demonstrated by 

 staining the part lined by it with silver nitrate, which brings into view 



the intercellular cement sub- 

 stance. 



It is found that when a 

 small portion of a perfectly 

 fresh serous membrane for 

 example (fig. 20), is im- 

 mersed for a few minutes in 

 a solution of silver nitrate, 

 and exposed to the action of 

 light, the silver is precipi- 

 tated in some form in the 

 intercellular cement sub- 

 stance, and the endothelial 



cells are thllS pped out 



by fine, dark, and generally 



sinuous lines of extreme delicacy. The cells vary in size and shape, and 

 are as a rule irregular in outline; those lining the interior of blood- 



Fig. 19. -Pigmented epithelial cells from the retina. 



Fig. 20. A piece of the omentum of a cat, stained in silver nitrate. X 100. The tissue forms a 

 "fenestrated membrane,' 1 ' 1 that is to say, one which is studded with holes or windows. In the 

 figure these are of various shapes and sizes, leaving trabeculae, the basis of which is fibrous tissue. 

 The trabeculse are of various sizes and are covered with endothelial cells, the nuclei of which have 

 been made evident by staining \vith haematoxylin after the silver nitrate has outlined the cells by 

 staining the intercellular substance. (V. D. Harris.) 



vessels and lymphatics being spindle-shaped with a very wavy outline. 

 They inclose a clear, oval nucleus, which, when the cell is viewed in 

 profile, is seen to project from its surface. The nuclei are not however 

 evident unless the tissue which has been already stained in silver nitrate, 



