Renal Function in Man 29 



theory of functioning more or less independently. We may 

 assume a priori that the blood flow to any nephron can be 

 varied by physiological means, and that at a given blood flow 

 the quantity of filtrate separated at the glomerulus can be 

 varied by local changes in intraglomerular pressure, due, 

 among other things, to changes in afferent and efferent ar- 

 teriolar tone. It is conceivable that a glomerulus may be 

 completely cut out of the circulation by local vasoconstric- 

 tion, while the appended tubule continues to function in 

 various excretory operations in the manner of the normal 

 aglomerular nephron; or that blood can be shunted away 

 from both glomerulus and tubule, rendering the entire neph- 

 ron inactive. And conceivably the destruction of glomeruli 

 or tubules may be effected separately during the course of 

 disease. 



It will simplify our subsequent discussion if we define in 

 terms of the physiology of the individual nephron the chief 

 deviations from normal function which may be expected to 

 occur. 



1. We will designate as normal active nephrons those 

 nephrons which possess both normal glomeruli and tubules. 



2. The term, aglomerular tubules may be used to desig- 

 nate nephrons of which the glomeruli have ceased to func- 

 tion for any reason, but in which the tubule is functionally 

 intact and receiving an adequate supply of blood, and is cap- 

 able of carrying on excretory operations. 



3. Any nephrons which, though potentially capable of 

 normal function, are excluded from function by ischemia 

 we will designate simply as inactive nephrons. 



4. The terms impotent tubules we can apply to nephrons 

 in which the glomerulus remains intact and active, but the 



