1922.] * Renal Portal’’ System. 133 
Cushny suggests that one reason why, when pressure in 
the glomerular capillaries is raised by increased resistance in 
the post-caval, the output of urine is not increased (when in 
living animals the arterial flow is retarded by constriction of 
the renal vein the urine decreases in quantity) is because the 
capsular epithelium becomes asphyxiated by the retardation of 
the blood flow, and he adds that the capsule epithelium 
‘responds rapidly” to such asphyxia. ‘To this suggestion I 
may reply that, as shown by the well-known examples of the 
frog’s lung and the abdominal skin of the frog, the more mori- 
bund an epithelium the more easily it filters, and Cushny himself 
(p. 101) refers to Sollmann’s demonstration that the “dead” 
kidney can produce a plentiful “exudate”? when the pressure 
of the perfusion fluid is raised ; moreover there is no evidence 
tion of the colloids remaining in the blood and therefore to 
an increase of the osmotic resistance offered by these 
colloids to further separation from the non-colloids, but this 
given such a pressure producing swollen veins, the tubules 
cannot only secrete urine, but can secrete urine at a much 
greater rate than when the veins are not swollen, provided 

(Amounts perfused per (Exp. 2) 56°5 c.c.—71 
c.c.—66 c.c. 
30 minutes) (Exp. 3) 35°5 c.c.—42°5 
C.c. 
—102 ¢.c.—100 c.c. 
Rate of Urine Output =(Exp. 1) 0°87 c.c.—1-4 
(Amounts secreted in c.c,—0'5 c.c.—0°33 c.c. 
30 minutes) (Exp. 2) 0°72 c.c.—1°4 
e c.-—1°25 c.c. - 
(Exp. 3) 0°7 c.c.—0°75 ¢.c 
—0°41 ¢.c.—0°36 c.c. 
(Exp. 4) 0°75 c.c.—0°62 
e.c.—0°55 c.c.—0°62 e.c. 
