936 



HUMAN ANATOMY. 



foci for its distribution to other parts of the system. The nodes therefore, serving 

 as traps for the infective material, possess a high degree of importance from the 

 surgical standpoint, an accurate knowledge of their location and of the lymph-paths 

 along which each group is situated being of great value. 



In addition to the ordinary lymph-nodes there occur in various regions of the 

 body, especially in the prevertebral regions of the abdomen, structures which 

 resemble lymph-nodes in their form and size, but differ from them in color. In 

 general the lymph-nodes are of a pale pinkish color, although those in the vicinity 

 of the lungs are usually blackish, from the deposition in them of dust particles from 

 the lungs, and those in connection with the vessels arising from the small intestine are 

 milky white during digestion. The structures in question, however, are of a deep 

 red color, owing to the presence of abundant blood-vessels in their cortical portion. 

 These bodies have been termed the hemolymph nodes, but their exact nature and 

 function have not yet been definitely ascertained. By some they are regarded as 

 special structures, quite different from the lymph-nodes, perhaps partaking somewhat 

 of the character of the spleen ; while others regard them as ordinary lymph-nodes 

 with an especially rich blood supply, transitional forms between them and the usual 

 lymph-nodes being believed to exist. Whether or not direct communication exists 

 between the cortical blood-vessels and the medullary lymphatics within these 

 hemolymph nodes is also a question concerning which differences of opinion exist. 

 Structure of Lymphoid Tissue. — Wherever found, whether as diffuse masses, 

 simple nodules, or as the larger and more complex lymph-nodes, lymphoid or adenoid 



tissue is composed of two chief con- 

 FiG. 787. stituents, the supporting reticulum 



and the lymphoid cells contained 

 within the meshes of the framework. 

 The reticulum varies in the thickness 

 of the component fibres and the size 

 of its meshes, but in the denser types 

 of lymphoid tissue, as seen in the 

 periphery of the solitary nodules and 

 in the cortical follicles and medullary 

 cords of the lymph-nodes, it is so 

 masked by the innumerable over- 

 lying cells that only after removal 

 of the latter can the supporting 

 framew'ork be satisfactorily demon- 

 strated. The reticulum, the nature 

 of which is still a subject of discus- 

 sion, may be regarded as modified 

 fibrous connective tissue, upon the 

 trabeculae of which, particularly at 

 the points of junction, flattened con- 

 nective tissue cells are closely applied 

 as a more or less complete invest- 

 ment. In certain localities where of 

 exceptional delicacy, the reticulum 

 may be formed almost entirely by 

 the anastomosing processes of stellate 

 connective-tissue elements. 

 The cells composing lymphoid tissue, exceedingly numerous and closely packed, 

 present the general characteristics that distinguish the lymphocytes, being small 

 elements with comparatively large nuclei, which exhibit a strong affinity for nuclear 

 (basic) stains. 



The simple lymph-nodules, of varying size but seldom more than 2 mm. in 

 diameter, are irregularly spherical or elliptical masses of lymphoid tissue in which a 

 denser peripheral zone encloses and blends with a core of less compact texture. 

 Within the looser and therefore lighter central area, lymphoid cells in various stages 

 of mitotic division are frequently seen, such foci, known as germ-centres, indicatmg 



Mucous 



glands 





Geim-centrt- 

 of nodule 



'Smmm 



~ Submucous 

 layer 



'■> .'./.^.,v,fi*V. •'^-* '^--. 



■'::'■ .V-fJ^v 



Simple lymph-nodule from large intestine. X 120. 



