The call for oxygen considered as a physiological test 111 



in the blood exercised an osmotic pressure of about 25 30 mm. of 

 mercury. In so far as filtration could account for the flow of urine, 

 filtration could only take place and therefore urine could only flow 

 when the capillary blood pressure was greater than 25 mm., since the 

 proteins do not go through the wall of the glomerulus. In short the 

 available pressure for filtration is the difference between the capillary 

 blood pressure and the osmotic pressure of the proteins of the plasma. 

 A necessary corollary to this clearly is that if you dilute the proteins 

 and therefore lower their osmotic pressure you increase, other things 

 being equal, the available pressure for filtration. 



The issue between these two explanations was taken up by 



o-H 



0-05- 



&> 



.5 



Rabbit. 



I 



Caffeine 



"T ' i 



900 



Caffeine 



FIG. 64. 



talfeine. Canine. 



FIG. 65. 



Oxygen and urine plotted as in Fig. 60. 



Knowlton (3) . His experiments may be summed up very shortly ; 

 always obtaining a diuresis which produced no work on the part of 

 the kidney. He showed : 



(1) That if gelatine was put in the Ringer's fluid in such quantity 

 that osmotic pressure of the gelatine was approximately equal to that 

 of the proteins of the plasma, while the viscosity of the solution was 

 approximately that of defibrinated blood, relatively little diuresis 

 was produced. This is seen in the chart given in Fig. 66. Three 

 injections were made : 



(a) Ringer's solution without gelatine. 



(b) Ringer's solution and 5 / gelatine. 



(c) Ringer's solution with gelatine. 



