KIMTUELIUM 83 



stained with haematoxylin (stain 5, p. iq). The specimen should be mounted 

 in glycerin. Wavy black lines indicate the intercellular cement substance. The 

 nuclei of the mesothelial cells are stained blue, those of the underlying connec- 

 tive-tissue cells a paler blue. It must be borne in mind in studying this specimen 

 that the strands or trabecular of the omentum are not composed of mesothelium, 

 but of fibrous connective tissue, and that the flat mesothelial cells merely lie 

 upon the surface of the connective-tissue strands. 



8. Endothelium may be demonstrated by removing the bladder from a 

 recently killed frog, distending it with air and subjecting it to the same technic. 

 By this means the intercellular substance of the endothelium of the blood-vessels 

 of the bladder wall is stained and the outlines of the cells are thus shown. 



