EFFECTS OF SECRETION ON THE HEART AND VESSELS. 17 



by the loss of the vasomotor center, and cause contraction 

 of the vascular walls by a direct action upon them. For the 

 time being, therefore, we can only conclude that, while injections 

 of suprarenal extract may cause cardiac and vascular contraction 

 by directly stimulating the muscular elements of these organs in 

 an animal from which the vasomotor center has been removed, it 

 probably stimulates the vasomotor center in a normal animal. 



ACTION OF THE ADRENAL SECRETION UPON THE HEART. 

 We have seen that destruction of the medulla and cord and 

 section of the cardiac nerves in the neck does not prevent 

 the rise of blood-pressure; the vasomotor center being thus func- 

 tionally eliminated, it is clear that constriction of the vessels 

 does not occur under these conditions, as a result of impulses 

 transmitted through them. Such being the case, it becomes a 

 question whether Oliver and Schafer's explanation in respect 

 to slowing of the heart by suprarenal extract namely: that 

 it is due to reflex inhibition of this organ through the constric- 

 tion of the arterioles induced still holds. We must not over- 

 look, in this connection, the fact that the active agency through 

 which the heart is slowed, according to their view, is not the 

 suprarenal extract, but the impulses from the center to which 

 the reflex inhibition is attributed, and it is plain that in the 

 absence of this center "inhibition" cannot occur. Hence, as 

 slowing of the heart takes place when this center has been re- 

 moved, it must be due to some other cause. 



Suprarenal extract, if its action is similar to that of the 

 secretion of the adrenals, should, it seems to us, be regarded 

 as a physiological agency, and not be confounded with toxics 

 which pervert normal conditions, nor with elements foreign to 

 existing structures. Considered from this standpoint, the ad- 

 dition of a given proportion of glandular substance to the sum- 

 total of that contained in the organism, or the removal of some 

 by any method, should involve a corresponding augmentation 

 or a diminution of the normal manifestations that represent 

 suprarenal functions, whatever these may be. The injection 

 of suprarenal extract, we have seen, produces a rapid and 

 marked increase of blood-pressure by stimulating the cardiac 

 and vascular muscles. When, therefore, we speak of stimulating 

 these structures we imply contraction of the muscular fibers 



