ORIGIN OF LYMPHATIC VESSELS. 377 



On the other hand in the more solid organs the lymphatic vessels occupy the 

 interstices of the organ, and in many cases lose in great measure their character of 

 distinct tubular canals, and appear simply as cleft-like spaces ; these are, however, 

 always bounded by an endothelial layer, like that which lines the lymphatic vessels 

 elsewhere. 



The lacunar mode of origin of, lymphatics was first described in the testicle by 



Fig. 436. LYMPHATIC PLEXUS OF CENTRAL TENDON OK DIAPHRAGM OF RABBIT, PLEURAL SIDE. 



(Klein.) MAGNIFIED. 



a, larger vessels with lanceolate cells and numerous valves ; b, e, lymphatics of origin, with wary- 

 bordered cells. Here and there an isolated patch of similar cells. 



Ludwig and Tomsa, and it is now known to be characteristic of most glandular 

 organs. Occupying everywhere the interstices of the penetrating connective tissue, 

 the lymph bathes the exterior of the tubules or alveoli of the gland, in many parts 

 even separating them from the capillary blood-vessels, so that the exchanges of 

 material between the plasma of the blood and the secreting cells of the gland must 

 be carried on through the intermedium of the lymph in these spaces. A network of 



