238 THE DUCTLESS GLANDS 



ules of the medullary protoplasm there are coarse structures 

 which occur on the side of the cells turned towards the vessels, 

 and which reveal a different staining reaction from the gran- 

 ules. The capillaries are everywhere bounded by endothelium 

 between the blood and the medullary cells. 



Thus it would appear that the evidence physiological and 

 histological that the adrenal medulla is, in fact, an internally 

 secreting gland, and that adrenin is the product of its secretion 

 is not very convincing. We have next to inquire whether 

 adrenin acts directly upon the sympathetically innervated 

 tissues, or whether it acts in some other more indirect or round- 

 about manner. Several writers believe that the function of the 

 adrenal medulla is to render harmless the poisonous products 

 of muscular activity, and render them serviceable for the regula- 

 tion or the nourishment and innervation of the whole motor 

 apparatus. Some are of the opinion that the waste products of 

 muscular metabolism are, in fact, converted into adrenin. 

 Thus the antitoxic theory is combined with that of internal 

 secretion. 



Notwithstanding the paucity of good evidence, clinicians and 

 pathologists have now very generally adopted the internal 

 secretion theory of the adrenal medulla, and the chromaphil 

 or " hypertensive " system generally. Thus, Rolleston dis- 

 cusses the possible pathological relations of the internal secre- 

 tion, and divides these into (1) Alteration in quantity (a) 

 absence, (b) diminution, and (c) excess ; and (2) alteration in 

 quality. There is no need to pursue this subject further. 



2. Theories as to the Function of the Adrenal Cortex 



We cannot at the present time allocate any definite function 

 to the cortical portion of the adrenal body, though there can 

 be little doubt that it exercises a very important influence 

 upon the economy. The cortex is larger than the medulla, and 

 is composed of epithelial cells, the appearance and micro- 

 scopical structure of which suggests a high degree of secretory 

 activity. Moreover, as we have seen (p. 152), there are strong 

 reasons for thinking that the cortex is of more importance for 

 the maintenance of life than the medulla. 



The presence of fatty or fat -like substances in the cortical 

 cells has been known for a long time, and has already been 



