HISTOLOGY 53 



polyhedral cells arranged in a network. These cells have a 

 finely granular cytoplasm. In the intercellular meshes are 

 sinusoids which allow an intimate contact between the cells 

 and the venous blood. In many places the endothelial lining 

 of the blood sinuses is in direct contact with the chromaphil 

 cells and, according to some observers, is completely absent. 

 There is a loose network of supporting connective tissue con- 

 taining smooth muscle fibers throughout the medulla. The 

 medulla is supplied with many non-medullated nerve fibers 

 and an occasional sympathetic ganglion. 123 



The extra-adrenal chromaphil tissue resembles closely that 

 of the adrenal medulla. Both tissues stain characteristically 

 with bichromate due to the presence of epinephrine. The 

 cell columns are thicker in the adrenal than in the abdominal 

 chromaphil bodies. The blood spaces are also wider in the 

 medulla and, according to Vincent, 648 the medulla gives an 

 appearance of a higher organization than does the accessory 

 chromaphil tissue. The cytoplasm of the medulla is also 

 more distinctly granular than that of the abdominal chroma- 

 phil body. 



Some observers have described the presence of two types of 

 cells in the medulla of certain animals. Such an apparent 

 diversity in the cytological appearance of the cells is due in 

 some cases to poor fixation, as shown by Kolmer, 362 for the bats 

 ( Vesperugo noctula et pipistrellus) . However, Kolmer describes 

 two types of cells in the hamster (Cricetus frumentarius) , the 

 horse (Equus caballus), and other species. Both types of cells 

 show the chromaphil reaction. It is difficult to say what 

 significance, if any, is to be attached to the morphological dif- 

 ference between these two types of cells. 



The constant regeneration of new cells so characteristic of 

 the cortex is not observed in the medulla. However, mitotic 

 activity is observed, particularly in the hedgehog (Erinaceus 

 europeus) in which the cytological detail of the chromaphil 

 cells is most striking. 362 



