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HANDBOOK OF PHYSIOLOGY. 



lymphatics do not, however, pass through glands before entering the 

 thoracic duct. 



Structure. 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. 221 ), 

 the capsule sends inwards processes called trabeculcB in which the blood- 

 vessels are contained, and these join with other processes prolonged from 

 the inner surface of the part of the capsule covering the convex or outer 

 part of the gland; they have a structure similar to that of the capsule, 

 and entering the gland from all sides, and freely communicating, form 

 a fibrous supporting stroma. The interior of the gland is seen on sec- 

 tion, even when examined with the naked eye, to be made up of two 



FIG. 223. Diagrammatic section of lymphatic gland, a. Z., afferent; el., efferent lymphatics; 

 C, cortical substance; l.h., reticulating cords of medullnry substance; l.s., lymph-sinus; c., fibrous 

 coat sending in trabeculae, t.r., into the substance of the gland. (Sharpey.) 



parts, an outer or cortical (Fig. 221, c, c), which is light colored, and an 

 inner of redder appearance, the medullary portion (Fig. 221). In the 

 outer or cortical part of the gland (Fig. 223) the intervals between the 

 trabeculae are comparatively large, and form more or less triangular in- 

 tercommunicating spaces termed alveoli ; whilst in the more central or 

 medullary part is a finer meshwork formed by the more free anastomosis 

 of the trabecular processes. Within the alveoli of the cortex and in the 

 meshwork formed by the trabeculas in the medulla, is contained the 

 proper gland structure. In the former it is arranged as follows: occu- 

 pying the central and chief part of each alveolus, is a more or less 

 wedge-shaped mass of adenoid tissue, densely packed with lymph cor- 

 puscles ; but at the periphery surrounding the central portion and im- 



