450 



ANGIOLOGT. 



thin and bighly clastic, consisting of smooth muscular fibres 

 interlaced with areolar and elastic tissue. The internal coat is 

 merely a basement membrane of elastic tissue, covered by a 

 simple layer of endothelium. The coat of the small vessels, 

 lymph capillaries, consists of membranous and cellular layers. 



The lymphatic vessels are beaded in appearance, due to the 

 presence of valves in their interior, which aid the onward flow of 

 their contents. These generally consist of two semilunar flaps, 

 with an attached convex and a free concave border ; they are 

 most numerous in the proximity of the glands, and are always 

 found where the lymphatic trunks enter the blood-vessels. 



Lymphatic vessels may pass through two or more glands, or 

 ^ they may enter a central 



y . trunk without approach- 



ing any gland. 



LYMPHATIC GLANDS. 



The lymphatic glands 

 are small, round, or oval 

 in shnpe, varying in size 

 from a hemp seed to a 

 kidney bean; in colour 

 they vary much, but are 

 generally some modifica- 

 tion of pale red, reddish 

 brown, or groy. They 

 consist of a cortical sub- 

 stance covered externally by a fibrous capsule which sends trabecu- 

 lae within the gland, dividing it into numerous polygonal cavities, 

 callfed loculi or alveoli, which are filled with a whitish pulp 

 containing cells and nuclei, identical in character with lymph 

 corpuscles ; the deeper part of the gland is called the medullary 

 substance ; it also contains loculi and lymphoid tissue. The 

 loculi are lined by very delicate processes given cff from the 

 trabeculae, which divide them into very minute cavities com- 

 municating with each other, forming a spongy texture enclosing 

 the lymphoid tissue. The vessels, just before reaching the glands, 

 divide into the afferent vessels, or vaaa afferentia, which enter the 

 gland ; these subdivide into intricate plexuses, which open into 

 the spongy cavities, whence originate vessels which lead to those 



Fia. 109. "•".•■ 



Section of a Lymphatic Gland, a a, Capsule ; 6 6, Trabe- 

 culae of cortical portioa ; c, TrabectOsa of medullary por- 

 tion : d e, Lymphoid contents of loculi; //, Afferent 

 vessels ; ; g. Their confluence, leading to h, the efferent 

 vessel. 



