THE CIRCULATORY SYSTEM. 



117 



groups : first, small twigs which enter at the periphery and are dis- 

 tributed in the capsule and fibrous tissues of the trabecuta and the 

 medulla ; and, second, arteries which enter at the hilus, pass through 

 the sinuses, and are distributed in the lymphadenoid tissue of the 

 medulla and cortex. The veins follow the courses of the corre- 

 sponding arteries. The nerve-supply is meagre, and consists of both 

 medullated and non-medullated fibres. Their mode of termination 

 is not known. 



In the centre of the follicles the reticular tissue is more open and 

 the lymphoid cells less abundant than toward the periphery. Mitotic 

 figures are of frequent occurrence in lymphoid cells in this region, 

 and it is evidently a situation in which those cells actively multiply. 

 Further toward the periphery 

 the reticular tissue is closer 

 and very densely packed with 

 small lymphoid cells, to be- 

 come more open again and 

 freer of cells as it passes into 

 the reticulum of the sinus 

 (Fig. 100). This last reticu- 



FIG. 100. 



FIG. 101. 



Fig. TOO.- Portion of lymph-follicle from mesentery of ox. (Flemming.) z, peripheral zone 

 of small, closely aggregated lymphoid cells. To the right of these is a portion of the 

 germinal centre of the follicle, with larger cells, many of which are dividing. Opposite 

 Us a cell executing amoeboid locomotion, pz, pigmented cell, which has taken up colored 

 granules from outside; tk, dark chromophilic body, the nature of which has not been 

 determined. Such bodies occasionally occur in lymph-nodes, but their origin and sig- 

 nificance are unknown. 



Fig. 101. Section of a small portion of the reticulum of the sinus in a human mesenteric 

 node. (Saxer.) 6, 6, diagrammatic representation of a portion of the neighboring 

 trabecula. 



lum becomes continuous with delicate fibres given off from the 

 tissues of the capsule and trabeculse (Fig. 101). The distribution 



