82 Physiology of the Kidney 



pressure falls, the diastolic usually falling below its control 

 level, indicating that dilatation has occurred some place in 

 the arteriolar bed. During the pressor phase the renal plasma 

 flow may be substantially reduced, but during the subsequent 

 phase of reduced diastolic pressure the renal plasma flov/ in- 

 creases again and mounts to values substantially above the 

 control level. This renal hyperemia is accompanied by a de- 

 creased filtration fraction, indicating that it is a result of di- 

 lation of the efferent glomerular arterioles. The change in 

 filtration fraction is usually such as to just offset the increase 

 in plasma flow, so that the filtration rate remains almost un- 

 changed. Again, were one observing only the filtration rate 

 it might be inferred, quite erroneously, that no change had 

 taken place in renal function. 



After examining the effects of typhoid vaccine, we 

 turned to a particular sample of highly pyrogenic inuHn 

 (No. 268) as affording a superior method for producing renal 

 hyperemia in man. This particular sample of inulin will pro- 

 duce a marked renal hyperemia in doses of 50 mgm. intra- 

 venously."' In thus turning evil to good account, we are 

 utilizing the only method known to us for inducing renal 

 hyperemia, for no drug which we have tried has this effect. 



After adequate doses of pyrogen an increase in renal 

 plasma flow of 50 to 75 per cent can be expected, though 

 we have seen in a subject whose basal plasma flow averages 

 777 cc. per minute ( = 1204 cc. of whole blood) , a hyperemia 

 amounting to 1894 cc. of plasma (=3005 cc. of whole blood) 

 per minute, an increase of 244 per cent. 



"^This inulin is of course thoroughly sterilized by boiling before administration. The 

 pyrogenic activity of this particular sample is in striking contrast to the fact that when 

 completely non-pyrogenic as much as 100 grams of inulin may be given without renal or 

 systemic disturbance. 



