48 ANATOMY 



which have thus far been obtained. Many of the described 

 structures are probably only artifacts resulting from fixation 

 and staining. Particular attention has been paid to the mito- 

 chondria which assume an important part in the structure of 

 the cortical cells. In the glomerulosa of the guinea pig they 

 are so abundant as to constitute almost all of the cytoplasm. 301 

 They are present throughout the cortex. The significance and 

 function of the mitochondria, however, is still a mystery. The 

 Golgi apparatus of the adrenal has recently been studied by 

 Bourne. 78 



The adrenal of the living frog as observed microscopically 576 

 appears filled with small, evenly distributed yellow granules 

 which change to a globular form. By fluorescent light a fine 

 network of fibers are seen around the granular cells which dis- 

 appear on the appearance of the globular form. Pithing and 

 the injection of curare or mercuric chloride induce changes in 

 the structure of the cells indicative of a diminution of their 

 lipid content. These limited observations of Singer and 

 Zwemer 576 are deserving of a more thorough investigation with 

 the hope of obtaining a more normal histological picture than 

 can be derived from dead tissue. 



THE MEDULLA 



The chromaphil cells of the medulla differ in their morph- 

 ological arrangement in different animals. In some species 

 the medullary cells are arranged in compact bundles held to- 

 gether by strands of connective tissue; in others they are ir- 

 regularly scattered without any semblance of order. The 

 type of cell found in the medulla is also variable ranging from 

 a cylindrical to an irregular polyhedral type. 362 



In man and the common laboratory animals the cells of the 

 medulla are irregularly arranged without the suggestive form 

 observed in the cortex (c/. Figures 4 to 9). The medulla in 

 man is characterized by a rich content of elastic supporting 

 fibers. It is very vascular and is composed of large irregular 



