86 



Scientific Proceedings (48). 



and the injection of the dried filtrate dissolved in Ringer's solution 

 retains the constrictor substance, but it contains no vasodilator 

 for the kidney vessels. 



We are, therefore, led to the conclusion that serum contains a 

 constrictor substance which acts on the limb vessels, the kidney 

 vessels and the coronaries. In addition there is also present a 

 dilator substance acting specifically on the renal vessels. The 

 dilator substance is a proteid, the constrictor substance is not. 

 The perfused kidney after the injection of serum is subject to the 

 action of both a dilator and a constrictor substance. The dilator 

 is the more powerful and masks the action of the constrictor. The 

 constrictor substance becomes manifest after removal of the 

 dilator by boiling or by precipitation by alcohol. 



Is the constrictor substance described above the suprarenin 

 quotient of serum? Suprarenin, as is well known, causes con- 

 striction by stimulation of the sympathetic nerve fibers. If we 

 add apocodeine hydrochloride to the perfusion fluid we can para- 

 lyze the sympathetics and in this way render the preparation 

 insensitive to the strongest solutions of suprarenin. If, however, 

 we inject serum there is still produced almost as great a diminution 

 in the rate of outflow as before. We have thus evidenced that 

 the constrictor substance is not suprarenin, and further, that it 

 is a body which acts directly on the muscle coats. 



In regard to the dilator substance acting on the kidney we 

 have found that it still causes an increased outflow after the 

 injection of serum when the perfusion fluid contains apocodeine. 



Effect of plasma. — Plasma differs markedly in its action. If 

 hirudin plasma is injected into the vessels of the limb it produces a 

 much less constriction than does the corresponding amount of 

 serum. This result is dependent only upon the amount of supra- 

 renin it contains, for when the sympathetics are paralyzed the 

 injection of serum produces no change in the rate of outflow. 



On the kidney vessels, however, plasma produces an even 

 greater dilatation than does serum. 



The conclusions which we have been able to draw from these 

 experiments are as follows. 



1. That in both plasma and serum there is present a substance 

 which causes dilatation of the renal vessels. This substance is a 

 proteid. 



