THE KINETIC SYSTEM 199 



brain and the thyroid also are mutually active in the 

 conversion of energy, and that without the thyroid the 

 brain is impaired. We have seen also that adrenal 

 activity invariably accompanies the transformation 

 of energy, and that increased adrenal activity is pre- 

 vented when the connection between the brain and the 

 adrenals is interrupted. In other words, our experi- 

 ments have shown that every adequate stimulus which 

 causes brain-cell changes and which is sufficient to 

 cause the production of motion or heat in the organ- 

 ism, causes increased adrenal activity and histologic 

 changes in the adrenals, except when the adrenal 

 nerve supply has been divided, in which case the 

 application of kinetic stimuli causes neither increased 

 adrenal activity nor histologic changes in the adrenals. 

 Furthermore, when an animal is deeply narcotized 

 with morphia before the administration of a kinetic 

 stimulus there is no increased output of adrenin and 

 there are diminished histologic changes in the adrenals. 

 This evidence seems sufficient to warrant the con- 

 clusion that the adaptive activity of the adrenals is 

 largely if not wholly dependent upon the brain. 



Is the converse true? That is, is the relation be- 

 tween the adrenals and the brain reciprocal? In 

 crossed-circulation experiments 1 we proved that ad- 

 renin alone causes increased brain activity, manifested 

 by increased blood-pressure and hyperchromatism 

 of the brain-cells in the animal whose brain received 

 the adrenin. (Figs. 46, 47.) Animals whose adrenals 



1 In these experiments the circulations of two dogs were crossed 

 so that all the blood from the body of one passed through the head 

 of the other and vice versa. 



