194 



MANUAL OF PHYSIOLOGY. 



called. Here the lymph channels form a kind of sheath for the 

 minute bloodvessels, and pass along to the connective tissue form- 

 ing the adventitia. 



FIG. 87. 



Endothelium from serous surface wiihout stomata (nitrate of silver). 



The lymph vessels may also be said to commence on the surface 

 of serous membranes which are intimately connected with the 

 lymphatic system, and may indeed be regarded as nothing more 



FIG. 88. 



Endothelium from serous surface with stomata surrounded with granular 

 protoplasmic cells. 



than exaggerated lymph spaces. In most parts of the endothelial 

 surface of serous cavities are a number of so-called stomata, or 

 small apertures surrounded by a few cells, which differ from the 

 ordinary endothelial cells in every respect, and probably have 



