768 THE ADRENAL GLANDS 



acts independently of those from other glands. On the contrary, there is 

 undoubtedly a close association of function, so that we can not tell 

 whether a change of function observed after removal of some gland or 

 administration of some extract is a direct consequence of the experi- 

 mental procedure, or is induced by some secondary effect developed on 

 another endocrine organ. It will no doubt take many years before suf- 

 ficient data have been collected to enable us definitely to state what the 

 particular function of each endocrine organ may be. Since most progress 

 has been made in connection with the adrenal gland, it will be advan- 

 tageous to consider the functions of this gland first. 



ADRENAL GLAND 



In mammals the adrenal gland is composed of two parts, the cortex 

 and the medulla. The origins of these two are quite different, and though 

 in mammals they are intimately associated in anatomical position, in other 

 groups of animals they are more or less separate, being completely so 

 in fishes. This not infrequent separation of cortex and medulla, together 

 with their distinctive origins, suggests different functions for the two. 

 Experimental investigation supports this view. 



The Cortex 



The cortex on microscopic examination is seen to be composed of rows of epithelial 

 cells arranged more or less in columns except at the periphery, where they form glomeru- 

 lar masses, and next the medulla, where they assume a reticular formation. The cells 

 of the greater part of the cortex, unlike those of the medulla, contain no granules with 

 special staining qualities, but they do contain particles which are believed to be com- 

 posed of cholesterol esters and lecithin. In the cells of the reticular portion of the 

 cortex, however, pigment particles are not infrequently observed. The blood supply of 

 the cortex is not nearly so rich as that of the medulla, being represented by fine arterioles 

 which run inwards from the capsule towards the medulla in the connective tissue that 

 lies between the columns of cortical cells. Nerves similarly penetrate into the cortex, 

 some supplying its blood vessels and cell columns, but most of them proceeding to the 

 medulla. They are derived from a network of nerve fibers in the capsule of the organ, 

 and the nerve supply of this network comes partly from the suprarenal plexus, and partly 

 from the splanchnic nerve. Embryologically the cortex is developed from the cells of 

 the genital ridge, that is, from mesodermie cells. 



Very little is known concerning the function of the adrenal cortex al- 

 though there is little doubt that it is closely related to the development 

 of the sexual organs. The evidence for this is as follows: (1) Its origin 

 from the mesoderm in common with the sexual organs. There is also 

 a remarkable similarity between the cortical cells and those of the corpus 

 luteum. (2) In cases of sexual precocity it is found that the adrenal 

 cortex is much hypertrophied. Also, certain tumors of the cortex occur- 

 ring in young children are associated with premature development of the 



