CH. xxn.] LYMPHATIC GLANDS. 313 



The lymph that leaves these tissues is richer in lymph-cells than 

 that which enters them. 



When lymph is collected from the thoracic duct after a meal 

 containing fat, it is found to be milky. This is due to the 

 presence in the lymph of minutely subdivided fat particles 

 absorbed from the interior of the alimentary canal. The lymph 

 is then called chyle. The fat particles constitute what used to be 

 called the molecular basis of chyle. If the abdomen is opened 

 during the process of fat absorption, the lymphatics are seen as 

 white lines, due to their containing this milky fluid. They are 

 consequently called lacteals. 



The structure and arrangement of the lymphatic vessels, are 

 given in Chapter XVIII., and we have now to proceed to the 

 study of the structure of 



The Lymphatic Glands. 



Lymphatic glands are round or oval bodies varying in size 

 from a hemp-seed to a bean, interposed in the course of the 



fig. 292. Section of a mesenteric gland from the ox, slightly magnified, a, Hilus ; b (in 

 the central part of the figure), medullary substance; c, cortical substance with 

 indistinct alveoli ; J, capsule. (Kolliker.) 



lymphatic vessels, and through which the lymph passes in its 

 course to be discharged into the blood-vessels. They are found 

 in great numbers in the mesentery, and along the great vessels 

 of the abdomen, thorax, and neck ; in the axilla and groin ; a few 

 in the popliteal space, but not further down the leg, and in the 

 arm as far as the elbow. 



A lymphatic gland is covered externally by a capsule of 

 connective-tissue, generally containing some unstriped muscle. 

 At the inner side of the gland, which is somewhat concave 

 (hilus), (fig. 292), the capsule sends inwards processes called 

 trabeculoR in which the blood-vessels are contained, and these 

 join with other processes prolonged from the inner surface of the 



