770 THE ADRENAL GLANDS 



times called the boundary zone, is much hypertrophied in the human fetus, 

 but this hypertrophy entirely disappears after the first year of extrauterine 

 life. 



The other functions of the cortex are not as yet known, but there is very 

 strong evidence that they are of great importance to the welfare of the 

 animal. It has been suggested that the passage of blood through the 

 cortex before reaching the medulla indicates that some change, which 

 is preparatory to the main change occurring in the medulla, takes place 

 in the blood while it is in the cortex. This view is partly substantiated 

 by the observation that when an excised jportion of cortex is incubated 

 at body temperature, a substance develops in it which has an action 

 like that of the hormone of the medulla epinephrine. It is possible, 

 however, that this action is due to the fact that certain of the decomposition 

 products of protein develop an epinephrine-like action (see page 536). 



A detoxicating function has been ascribed to the cortex. This possi- 

 bility has been suggested by the fact that cobra venom, to which had 

 been added an emulsion of this portion of the gland, was rendered innoc- 

 uous. (Meyers). 5 The addition of other tissue extracts to the poison 

 was without effect. 



The weight of evidence favors the view that it is the cortex and not 

 the medulla which is essential to life. Biedl 2 claims to have removed the 

 cortex leaving the medulla intact ; the operation resulted invariably in 

 the death of the animals. Conversely he found that, in cats and dogs, 

 the adrenals could be removed with impunity to the extent of seven 

 eighths of their bulk, provided that the portion remaining consisted of 

 cortex. Wheeler 6 endeavored to remove the medulla, leaving the cortex 

 intact ; though this was not wholly successful, it is a noteworthy fact that 

 it was those animals only, in which the cortex was inadvertently injured, 

 that succumbed to the operation. Evidence for the indispensability of the 

 cortex is also offered from the clinical side. Cases of acute adrenal de- 

 ficiency, followed by rapid death, occur, in which the medulla, postmor- 

 tem, shows few or no lesions or disease of a longstanding nature, whereas 

 acute lesions are observable in the cortex. 



The Medulla 



Histologically the medulla is composed of masses of polygonal cells 

 with blood sinuses between them. The blood supply is derived from ves- 

 sels that have proceeded to the medulla through the capsule, and it is 

 extremely rich, being indeed the richest blood supply to any organ in the 

 body, greater even than that to the thyroid gland. The nerves form a 

 dense plexus, extending into and between the secretory cells. The most 

 characteristic feature of the cells composing the medulla is the presence 

 in them of granules which stain readily with chromic acid, and are hence 



