234 THE DUCTLESS GLANDS 



appear very extraordinary if stimulation of the splanchnic 

 caused vaso-dilation in the adrenal bodies, while it caused vaso- 

 constriction in all the other abdominal viscera to which it sends 

 fibres. Moreover, the experimental evidence on this point is 

 not satisfactory. We might even go as far as to assume for the 

 present that stimulation of the splanchnic constricts the vessels 

 of the adrenal body. If this is the case, the constriction of the 

 vessels of the gland might actually be the cause of the discharge 

 of adrenin. For a certain amount of this substance contained 

 in the veins and capillaries of the organ would be almost 

 instantly driven out into the general circulation. This effect 

 could, of course, be only of the briefest duration, though it might 

 easily be sufficiently prolonged to produce the temporary effects 

 above referred to. These effects, as we have seen, consist prac- 

 tically in a fall of the carotid blood -pressure and a constriction of 

 vessels in certain somatic areas. This theory would account for 

 the fact, observed by Elliott, that it is not possible to exhaust 

 completely the gland by continued splanchnic stimulation. 

 It would also explain the fact that the effects above detailed 

 cannot be repeated until a certain time has elapsed since the 

 first stimulation. If this were found to be the true explanation 

 of what happens, we should then not have to deal with a true 

 secretory activity of the glands, but only a mechanical expul- 

 sion of adrenin as a result of vaso-constriction. 



In all such discussions it is important to bear in mind that 

 the medulla of the adrenal body constitutes only a portion of 

 the total chromaphil tissue in the body. In fact, it seems more 

 than likely that there is more chromaphil tissue outside the 

 adrenal bodies than within them. We can scarcely avoid this 

 conclusion when we remember that the tissue in question is 

 distributed widely in the sympathetic ganglia and in masses 

 of various sizes throughout the abdomen. 



This being so, it is remarkable that elimination of the adrenal 

 medulla alone produces such marked and definite results as 

 we have described. In the case of the effects of stimulation 

 of the splanchnic nerve, it may be that the stimulation produces 

 greater or more direct effects on the adrenal medulla than on 

 such structures as the " abdominal chromaphil body," though 

 the innervation of the latter would also be from the splanchnic. 

 There is another possibility. Assuming that the glandular 

 theory of adrenal activity is the true one, it might be urged 



