THE ADRENAL BODIES 213 



the fact that the medulla of the adrenal body is not the only 

 representative of the tissue which forms it (chromaphil tissue) ; 

 there are numerous scattered bodies of the same nature in close 

 relation to the sympathetic ganglia and nerves in different 

 regions of the body. In lower vertebrate animals the medulla 

 (chromaphil bodies) and cortex (inter-renal bodies) form two 

 separate and independent systems, having no anatomical (and, 

 so far as we know, no physiological) relationship to each other. 

 Indeed, strictly speaking, the medullary substance is not part 

 of the adrenal body at all, but simply an accumulation of the 

 chromaphil tissue which has arisen from the sympathetic in a 

 certain region of the body, and has insinuated itself into the 

 adrenal proper, or what we call the " cortex." 



In discussing the function or functions of the adrenal bodies 

 these facts of comparative anatomy must not. for a moment be 

 lost sight of. The ultimate question which we have to solve is, 

 from the standpoint of comparative physiology, not so much 

 what is the function of the adrenal body or of its two constituent 

 portions, but what are the functions respectively of the inter- 

 renal system (cortical system) and the chromaphil system 

 (medullary system), which are, as we have seen, separate and 

 distinct in Elasmobranch fishes (Figs. 44, 45) ? It is difficult 

 to say whether we ought to expect that these functions should 

 be of a kindred nature, or in any way related to each other, in 

 the case of the mammals. There certainly would be no a 

 priori reason for suspecting the existence of any such relation- 

 ship in the Elasmobranch fishes, but we cannot overlook the 

 fact that phylogenetically and ontogenetically portions of the 

 two systems become attracted, so to speak, to each other, and 

 finally in the adult mammal form a single compound organ. 

 One cannot escape from the suspicion that the coming together 

 may have some significance affecting the functions of the gland 

 as a whole. We are, however, at present completely in the 

 dark as to any functional correlation between the two con- 

 stituents. It is possible, moreover, that cortex and medulla 

 have separate and distinct functions ; at any rate, most of the 

 accurate knowledge which we possess and nearly all our most 

 plausible hypotheses have reference to the medulla of the 

 organ, and this notwithstanding the fact that the cortex is 

 larger than the medulla, and more distinctly glandular in type 

 and appearance. 



