CHAPTER ]X. 



Structure of the Subepithelial Lymphatic Glands. 



All lymphatic glands, whether interstitial or sub- 

 epithelial are composed of a number of similar units. 

 Each unit is best called a lymph nodule, but has also 

 been termed a " lymph-follicle " or '' germ-centre." 

 The lymph nodules are the bricks of which the lymph- 

 atic workshops are built. The lymph nodules may 

 roughly be said to average the size of a pin's head 

 each. 



Each lymph nodule consists of a mesh-work of reti- 

 form tissue amongst which are densely crowded two 

 types of cells. 



First type. — In the centre of the nodule are found 

 large cells with abundant cytoplasm. The nuclei do 

 riot usually stain darkly. In ordinary haematoxylin- 

 eosin sections the centre of the nodule is much paler 

 than the periphery. These larger clear cells may also 

 be found sparsely in other parts of the nodule. Flem- 

 ming in 1885 described numerous kario-kinetic figures 

 in the nuclei of these large cells and hence he named 

 the nodules germ-centres. These cells possess highly- 

 developed phagocytic powers and may at times be seen 

 to contain soot-particles, bacteria, and even other cells. 

 ~ Second type. — Each cell is small in size with scanty 

 cytoplasm and a round darkly-staining nucleus. It 

 exactly resembles the small lymphocyte found in the 

 blood stream. These cells are far the more numerous, 



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