70 THE PHYSIOLOGY OF THE ADRENALS. 



heart, or even of muscle. Evidently, therefore, the great 

 affinity of the suprarenal extractive for oxygen caused it, as 

 had the salicylic aldehyde, to take up and fix the hepatic oxygen, 

 and the fact that in doing so it lost its activity appears to us to 

 indicate that its physiological functions are in some way con- 

 nected with this property. 



If the affinity of the suprarenal secretion for oxygen is the 

 source of its physiological activity, where would the useful 

 reaction occur? The first important vessel reached by the se- 

 cretion is the inferior vena cava. As veins contain blood which 

 has served its purpose in the organism, it is not likely that this 

 blood should be utilized otherwise than as a vehicle. Again, 

 that it is not in the blood of the vena cava that the secretion 

 undergoes a reaction is obvious; it enters the blood-stream 

 near the heart: i.e., where the proportion of oxygen is normally 

 at its lowest ebb. That this acts only as a carrier for the secre- 

 tion, therefore, is evident. Yet there is a very interesting and 

 suggestive feature connected with the itinerary of the secretion 

 and which bears directly upon the question in point. Biedl 

 and Szymonowicz undoubtedly found the secretion in the ves- 

 sels near the adrenals, but not in other veins of the organism. 

 Blood drawn from the suprarenal vein gave rise, when injected 

 into the blood-stream of a normal animal, to manifestations 

 similar to those observed after the injection of suprarenal ex- 

 tract, while injections of blood taken from other veins were 

 followed by negative results. The suggestive feature referred 

 to is that the limits of the organs in which the reaction must 

 occur become restricted to the neighborhood, as it were, of the 

 channels in which the secretion first appears. What are the 

 limits of this "neighborhood?" 



The inferior vena cava supplying nothing capable of sug- 

 gesting a reaction in its blood, the secretion must reach the 

 heart, and, if it does, its presence must in some way become 

 manifest, since we have seen how powerfully this organ re- 

 sponds to the action of suprarenal extract. But, of course, it 

 is necessary to ascertain whether it reaches the heart under 

 normal conditions. Digitalis, owing to its well-known action 

 upon the heart-muscle, suggests itself as a ready means for 

 this purpose. Indeed, its toxicology not only associates it di- 



