ORGANS OF THE BODY. 



411 



224. 



We now turn to the medullary portion of the lymphatic glands. 

 This may be looked upon in its complex nature as a continuation of 

 the cortical septa and the substance of the follicles with their investing 

 spaces and retinacula. 



Under microscopical analysis many varieties are observed to exist in 

 the nature of this portion of the gland, according to the age of the animal 

 from which the latter has been taken. Thus it is more fully developed 

 m younger, as a rule, than in older bodies, in which it appears more 

 or less degenerated. It is observed to differ also, to a certain extent 

 according to the species of 

 animal examined. Finally, 

 the medullary substance of 

 the lymph-nodes belonging 

 to the interior of the body, 

 and especially to the diges- 

 tive tract, as a rule, displays 

 a higher degree of develop- 

 ment than those situated 

 more superficially, as the 

 inguinal and axillary glands. 



Let us commence with 

 the septal system, formed of 

 connective-tissue. This (fig. 

 401, c), supposing it to be 



moderately developed, is the continuation of the interfollicular partitions, 

 and consists of fine, but dense, connective-tissue plates and bands, 

 uniting with one another at acute angles at intervals, or dividing in 

 the same way one from another. Eventually, in the neighbourhood of 

 the bilus, i.e., of that point at which the efferent 

 vessels leave the organ (b), the connective-tissue 

 septa converge and unite to form a common fibrous 

 mass. The latter again exhibits in its amount the 

 greatest variety imaginable. Whilst in many of 

 the internal lymph-nodes it is extremely insignifi- 

 cant, or even almost entirely absent, it may attain 

 enormous thickness in others, especially those lying 

 less deeply, encroaching upon the lymphoid tissue 

 of the medullary substance. 



To this massive fibrous structure, arising from 

 the union of the septa, the name of the connective- 

 tissue nucleus (Frey), or hilus-stroma (His) has been 

 given. 



Turning to the essential, i.e., lymphoid portion 

 of the medullary mass (e), we find it to be made up of cylindrical tubular 

 elements, which, connected with one another in a reticulated manner, give 

 rise to a peculiar spongy tissue, whose interstices correspond to prolonga- 

 tions inwards of the cortical investing spaces. We shall speak of these 

 cylindrical elements for the future as the lymph-tubes ("medullary tubes " 

 of His) and of the system of lacunae between these, under the name of 

 lymph passages of the medullary substance (cavernous passages). 



Let us now glance, in the first place, at the lymph-tubes (figs. 402, 



Fig. 402. Lymph tube f run 

 the mesenteric glands cf a 

 dog. a, capillary, 6, re- 

 ticular connective sub- 

 stance forming the tube. 



