THE RENAL CIRCULATION 



1463 



fig. 8. The relationship of the molecular 

 weight of dextran to percentage filtered. [After 

 VVallenius C326).] 



fig. 9. The juxtaglomerular 

 complex of the kidney. JGA: 

 juxtaglomerular apparatus (Pol- 

 kissen) ; MD : macula densa of 

 distal convoluted tubule. [Cour- 

 tesy of B. S. Garber (unpub- 

 lished).] 



appearance, and contain granules (periodic acid- 

 Schiff reaction) which vary in amount in various 

 forms of experimental hypertension and with varia- 

 tions in sodium intake. Pathological states which 

 produce renal ischemia, such as the crush syndrome, 

 cause similar changes and are accompanied by in- 

 crease in blood pressure (no). A role in the regulation 

 of autonomy has been invoked for this structure (121, 



274, 281, 308, 330). In general, when the kidney is 

 exposed to hypertensive blood pressures, the granu- 

 larity decreases; if the blood pressure is decreased, the 

 granularity tends to increase. Tobian (310) feels that 

 these cells act as "stretch receptors," changing their 

 rate of secretion inversely with degree of stretch of the 

 walls of the arterioles. 



The changes in granularity in the JGA cells are 



