80 Physiology of the Kidney 



gesting that the fundamental mode of action of adrenin and 

 ephedrine is quite different. (It is interesting in this con- 

 nection to refer to a recent discussion of the action of 

 ephedrine by Gaddum/^') Adrenin, as I have pointed out 

 above, acts apparently exclusively upon the efferent glomer- 

 ular arteriole. We have found no drug which acts ex- 

 clusively upon the afferent arteriole, though there is evi- 

 dence that afferent constriction plays an important part in 

 reflexly elicited ischemia. 



I turn now to experiments dealing with vasodilatation of 

 the renal arterioles. Early in our investigations we sought 

 some means of increasing the renal blood flow by vasodilata- 

 tion and in the past three years we have expended an extrava- 

 gant amount of time on this problem. May I remark in this 

 connection that when the experimenter fails to accomplish 

 a result which is rationally to be expected he is likely to be on 

 the threshold of a new discovery, and further, that he fre- 

 quently learns more from accidental adventures than from 

 well planned experiments. That we can finally report a 

 means of producing renal hyperemia in the human kidney in- 

 volves, in a sense, a new discovery about that organ, and the 

 discovery of the method of producing this hyperemia cer- 

 tainly rests upon a fortuitous circumstance. 



Inulin, which we use for measuring the filtration rate, is 

 physiologically inactive when properly prepared, as may be 

 demonstrated by the absence of any disturbance in renal 

 function, body temperature, blood pressure or subjective 

 feeling, in subjects receiving intravenous infusions over 

 periods of several hours. But early in our investigations we 

 encountered difficulty in obtaining suitable inulin, inasmuch 

 as some samples of it contain a powerful pyrogen, comparable 

 to the pyrogen present in typhoid vaccine and probably com- 



