200 MANUAL OF PHYSIOLOGY. 



transmit the ordinary transudation stream for nourishing the tis- 

 sues. They freely communicate one with another, and lead into 

 the beginnings of the network of lymphatic capillaries. 



The lymph capillaries run midway between the blood capilla- 

 ries, and are made up of a single layer of nucleated endothelial 

 cells, which can be brought to light with silver staining. 



In some tissues, such as that of the central nervous system, the 



FIG. 86. 



Clefts in the Corneal Tissue of a Frog treated with nitrate of silver, which leaves the 

 spaces clear and stains the intermediate structure. These clefts (a) and their processes 

 (5) form the lymph canalicular system, and at the same time are the spaces in which the 

 corneal corpuscles reside. (Klein.) 



liver and bone, the lymph vessels commence as channels encir- 

 cling the blood vessels, or perivascular lymph spaces, as they are 

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

 minute blood vessels, and pass along to the connective tissue 

 forming the adventitia. 



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

 of serous membranes which are intimately connected with the 



