EPITHELIAL AND ENDOTHELIAL TISSUE. 



315 



to the formation of inflammatory corpuscles, and also of new 

 epithelia (see papilloma in chapter on tumors). 



One of the favorite subjects for the study of endothelium 

 was the peritoneum. The same valuable re-agents which have 

 been of so much service in elucidating the minute structure of the 

 basis- substance of connective tissue, have also proved useful for 

 the revelation of the structure of the cement-substance. These 

 re-agents are the nitrate of silver and the chloride of gold. Von 

 Recklinghausen had demonstrated that the cement-substance, 

 under the influence of a one per cent, solution of nitrate of silver, 

 becomes dark brown, and that in the endothelia of the lymph-sacs 

 and that of the peritoneum circular openings appear, which lead 

 into the lymphatics, and in a very short time admit of the absorp- 

 tion of fine granules of carmine, aniline, etc., injected into the 



FIG. 133. ENDOTHELIAL INVESTMENT OF THE PERITONEUM OF A 

 CHICKEN, STAINED WITH NITRATE OF SILVER. 



K, knobs of small endothelia, along the blood-vessels ; V, capillary blood-vessels, coursing 

 in C, the connective-tissue layer of the peritoneum. Magnified 150 diameters. 



cavities. The so-called serous surfaces proved to be closed 

 lymph-sacs, which are in an open communication with the 

 lymph-vessels. It became known that the endothelia of the 

 peritoneum are of varying sizes, and E. Klein demonstrated 

 knob-like protrusions along the blood-vessels, connected with 

 the growth of the endothelia. (See Fig. 133.) 



The two surfaces of the free peritoneal membranes f. i., the 

 omentum, the mesentery exhibit endothelia differing in size, 



