Renal Function in Man 7 



in man which afford convincing evidence that a process of 

 glomerular filtration, identical with that in the frog, occurs 

 in man. 



Those who recall the details of Cushny's theory will recol- 

 lect that that writer was opposed to the belief that substances 

 could be excreted directly by the tubule cells into the tubular 

 urine without the interposition of the glomeruli. Cushny's 

 opinion on this matter was, I believe, influenced by the con- 

 viction that such a process of tubular excretion must involve 

 vital activity on the part of the tubule cells, a vital activity 

 that transcended investigation and quantitation. In the pre- 

 vious century the doctrine of vitalism had been expelled from 

 the physiology of nerve and muscle and, commendably, 

 Cushny had no wish to see it regain a foothold in the physi- 

 ology of the kidney. Subsequent investigations, however, 

 have not only demonstrated that tubular excretion actually 

 occurs, but they have shown that this tubular process, far 

 from being vitalistically indeterminate, is amenable to or- 

 derly, quantitative description. Recalling the many years 

 during which the very existence of tubular excretion was 

 vigorously denied by adherents of the Cushny theory, we 

 may note that so far as affording us information on critical 

 aspects of renal activity, this process of tubular excretion is 

 of much greater importance than is glomerular function. 



The first convincing evidence of tubular excretion ap- 

 pears to have been adduced by Marshall and Vickers from a 

 study of the excretion of phenol red in the dog, but the most 

 emphatic evidence consists of observations of Marshall and 

 Grafflin and of Edwards and Condorelli on the aglomerular 

 fish kidney. For the details of investigations on the aglom- 

 erular kidney we may refer to the summaries of MarshalP^ 

 and Shannon.^^ It will suffice to point out here that the 



