644 INTERNAL SECRETION 



ological actions, so that the formation of this compound seems to be a 

 property common to chromaphil tissue, no matter what its situation 

 may be. A remarkable fact, and one calculated to induce caution 

 in assigning a physiological function to epinephrin, is that the so-called 

 parotid gland of a Jamaican toad secretes it in a concentration not 

 much short of 5 per cent. (Abel). 



Function of the Adrenal Cortex. The function of the cortical 

 cells is very obscure, but there is some evidence that they, and not 

 the chromaffin cells of the medulla, are concerned in the production 

 of the internal secretion, whatever its nature may be, the loss of 

 which leads so speedily to death on removal of the adrenals or in 

 the neutralization of poisonous products if that is the essential 

 thing. For example, the period of survival after this operation is 

 practically unaffected by the continuous intravenous adminis- 

 tration of adrenalin, although the loss of the medulla might be 

 supposed to be compensated in this way. In Addison's disease 

 adrenalin is likewise powerless. When the adrenals are not com- 

 pletely extirpated, compensatory hypertrophy of the remaining 

 portions may occur, and the animal survive indefinitely. In such 

 cases it has been found that the hypertrophy is confined to the 

 cortex. The weakness (asthenia) of the skeletal, and to some 

 extent of the cardiac, musculature which is characteristic of Addi- 

 son's disease, is produced experimentally within a few hours by 

 ligation of both adrenals. It is stated that the cortex contains 

 cholin, a substance which lowers the blood-pressure, instead of 

 raising it, as adrenalin does. It has been suggested that the adrenal 

 glands have thus a double chemical grip upon the circulation, and 

 can influence it in either direction, just as the bulb can influence it 

 through its double nervous grip. But it is possible that the depres- 

 sor substance of the cortex may be only a toxic body neutralized 

 or destroyed in the glands. In any case the functional difference 

 between cortex and medulla is easily understood when we reflect 

 that the morphological history of the two tissues is quite different. 

 The medulla is developed from cells which push their way into the 

 gland from the rudiments of the sympathetic ganglia at that level, 

 and is therefore of ectodermic origin. The cortex is derived from 

 the same mesodermic structure which gives rise to the kidneys and 

 genital organs. . 



{ Pituitary Body or Hypophysis.Hln the pituitary body two parts 

 essentially different in origin and Junction may be distinguished:/ 

 (i)I The large anterior lobe, ot-jiars^aaterior, consisting of epithelial 

 cellsj many of which are filled with granules of the type seen in 

 glandular epithelium, and abundantly provided with bloodvessels; 

 (2)tthe smaller posterior or nervous lobe, or pars nervosa, also 

 called the infundibular portion, consisting chiefly of neuroglia, the 

 whole connected with the floor of the third ventricle by a stalk 

 called the infundibulum. 



