12-1 



NORMA L HISTOLOG Y. 



of the lymphoid cells gives the follicles a general concentric appear- 

 ance. 



The lymph-follicles of the cortex not infrequently blend with 

 each other, and the activity of the cellular reproduction in their 

 centres varies considerably and is sometimes entirely wanting, when 

 the concentric arrangement of the cells disappears. 



The structure of the lymph-nodes causes the lymph entering them 

 to traverse a series of channels, the " sinuses," which, in the aggre- 

 gate, are much larger than the combined lumina of the vessels sup- 

 plying them. The velocity of its current is, therefore, greatly re- 

 duced, and it remains for a considerable time subjected to the action 

 of the lymphoid cells in and near the sinuses. Small particles which 

 may have gained access to the lymph in its course through the tis- 

 sues are arrested in the lymph-nodes, and are either consumed by 

 phagocytes — i. e., cells possessing the power of amoeboid move- 

 ment and capable of incorporating foreign substances — or are con- 



Fig. 109. 



Section of red marrow; human. (Bohm and Davidoff.) a, a, ery throblasts ; b, b, myelocytes ; 

 6'. myelocyte undergoing division : c, giant-cell with a single nucleus ; c', giant-cell with 

 dividing nucleus; d, reticulum ; < , space occupied by a fat-cell (not represented);/, gran- 

 ules in a portion of an acidophilie cell. 



veyed into the marginal portions of the follicles, where, if insus- 

 ceptible of destruction, they remain. It is in consequence of this 

 process that the lymph-nodes connected with the bronchial system 



