Chap. XII.] THE VASCULAR SYSTEM. 



147 



the contents of most of these vessels have to pass in their prog- 

 ress towards the thoracic and right lymphatic ducts. These 

 bodies are collected in numbers alongside of the great muscles 

 of the neck, and also in the thorax and abdomen, especially in 

 the mesentery, where they are called the mesenteric glands, and 

 alongside of the aorta, vena cava inferior, and the iliac vessels. 

 A few, usually of small size, are found on the external parts of 

 the head, and considerable groups are situated in the axilla, 

 and also in the groin where they receive the name of inguinal 

 glands. Some three or four lie on the popliteal vessels, and 

 usually one is placed a little below the knee, but none farther 

 down. In the arm they are found as low as the elbow joint. 



The size of the lymphatic glands is very various, some being 

 not much larger than a hemp seed, and others as large as an al- 

 mond, or even larger than this. In shape, they are usually oval. 



A lymphatic gland is covered by an envelope, or capsule, of 

 connective and muscular tissue. This capsule sends fibrous 



Fio. 103. — Diagrammatic Section of Lymphatic Gland. (Sharpey.) a.L, 

 afferent lymphatic: e.I.. efferent lymphatic; c, capsule, or envelope; </-, trabeculse ; 

 ^5, lymph-sinus; l.h, pulpy substance of gland. 



bands (trahec\dce) into the substance of the gland, dividing the 

 exterior portion into more or less regular compartments, and 

 the interior into irregular labyrinths. This framework is occu- 



