The Renal Blood Flow 87 



ous anastomoses between the arterial tree and the venous cir- 

 culation. Spanner believes that through these anastomoses a 

 retrograde tubular circulation can be maintained quite apart 

 from the glomerular circulation. In any of these instances, 

 partial closure of the glomerular circulation might forcibly 

 deflect blood through these extraglomerular channels and ac- 

 tually increase the peritubular blood flow. On the other hand, 

 constriction of the direct arteriolar channels might induce 

 some degree of glomerular hyperemia while producing tubu- 

 lar ischemia. 



It is clear that one cannot a priori predict the effect of a 

 constrictor agent upon the renal circulation. In inquiring 

 into this question experimentally we have measured the num- 

 ber of active glomeruli by glucose-Tm, and the number of 

 active tubules by diodrast-Tm. In an experiment already 

 described (Figure 2), it was observed that adrenin did not 

 appreciably change glucose-Tm, which is an index of the 

 number of active glomeruli. In that experiment diodrast-Tm 

 was omitted so that we could follow the renal plasma flow 

 during the action of the hormone, since during the measure- 

 ment of diodrast-Tm the tubules are saturated with diodrast 

 and the diodrast clearance no longer reflects the renal plasma 

 flow. Apart from this consideration it is possible to measure 

 both glucose-Tm and diodrast-Tm at the same time; if one 

 wishes to have a figure on the existing renal plasma flow, this 

 must be measured in advance of diodrast-Tm. 



Our usual method of examination is illustrated in Figure 

 6. This figure shows three groups of data: basal, during the 

 action of adrenin, and during hyperemia. Each heavy, solid 

 line represents the average of 4 or 5 clearance periods. In the 

 first half of each experiment the subject was prepared for 



