RENAL FUNCTION 



257 



individuals of Camharus clarkii. The essential data for our consideration 

 are contained in Fig. 7 of his report, which is reproduced here as Fig. 3. 

 It will be noted from the figure that the U/B inulin ratio, up to quite high 

 blood-inulin concentrations, is well in excess of 2 and reaches as high as 5. 

 Are these values the result of faulty technique? Maluf injected adequate 

 amounts of inulin ; it was distributed normally as indicated by the fact that 

 computations made by the writer show a blood volume of 25% of the 

 body weight, which checks w^ell with Prosser and Weinstein's (1950) de- 

 termination of the blood volume of this form; his analytical procedures 

 were capable of delivering the accuracy claimed; the injected inulin may 

 be nearly accounted for by the sum of the excreted inulin and that still 

 present in the blood of the animal at the end of the experiment ; the blood 

 samples were not too large for good physiological results ; and the urine 

 flow corresponded to that obtained by another investigator working wnth 

 the same species. 



9 Creatinine 



O ond • Inulin 



Xylose 



cP 



200 400 600 



Concentration 



eoo 1000 1200 1400 1600 laoo 

 Blood — mgm. per cent 



Fig. 3. Excretion of inulin, xylose, and creatinine by Camharus clarkii. Redrawn 

 from Alaluf, 1941. 



Two minor criticisms may be stated. In some experiments the excretory 

 pores were sealed, so that abnormal pressures might have been built up in 

 the bladders. Against this view is the fact that results of this series checked 

 those of an earlier series in which the pores were not sealed. Second, it 

 was necessary, in carrying out the blood collections during the experi- 



