110 Chapter VII 



Is this or is it not due to increased activity on the part of cells of 

 the kidney ? * 



The record of such an experiment is given in Fig. 62. The animal 

 which was the subject of the experiment was secreting 0'05 c.c. of 

 urine per minute, its blood pressure was 95 mm. of mercury ; 22 cubic 

 centimetres of blood were taken out and 25 c.c. of Ringer's solution 

 w r ere injected : the secretion at once rose to 0'4 c.c. per minute (see the 

 notch on the record of the diuresis at 12.23), the arterial pressure being 

 then but 52 mm. The suspension of corpuscles (25 c.c.) was put into 

 the jugular vein, the arterial pressure at once rose to 84mm., and the 

 diuresis reached the very large figure (for a rabbit) of 2'35 c.c. per 

 minute. The rate of flow of blood through the kidneys was slightly 

 slower in the diuretic period than before it, being 1 c.c. in 4'3 seconds 

 as opposed to 1 c.c. in 2'9 sees. The urine attained a value of 0'95 / 

 of chlorides during the diuresis, and the oxygen taken in presented 

 scarcely any variation. 



During 

 Before diuresis * , After 



Oxygen taken in per gram of kidney per minute 0-104 c.c. 0-108 0-105 0-09 



Similar results were obtained in a second experiment of the same 

 nature (Fig. 63). In it the oxygen taken in before the diuresis was 

 O'll c.c. per gram per minute, during the flow O'lO. 



At this point something may be said about the theory of caffeine 

 diuresis. Up to the present time two theories have been put forward 

 to explain it, (1) that the caffeine acts as a specific stimulant to the 

 kidney cells and (2) that it acts by causing vaso-dilatation, accom- 

 panied to some extent by a paralysis of the hypothetical reabsorptive 

 mechanism of the tubules. 



The idea that mere dilution of the protein constituents of the 

 plasma could cause a copious diuresis without any activity on the 

 part of the cells of the kidney was to us so interesting that we felt 

 bound to pursue it further. There seemed to be two possible ways 

 of explaining it. The first of these was that owing to the decreased 

 viscosity of the blood the pressure in the capillaries was greater than 

 formerly, the arterioles not damping the pressure to their normal 

 extent, and secondly, an explanation might be found by expanding 

 a conception put forward some years ago by Starling (2) . To explain 

 the fact that the flow of urine normally stops when the arterial 

 pressure is abnormally reduced, Starling pointed out that the proteins 



* The main points in the following discussion on the kidney have been confirmed 

 by the independent work of Prof. Tangl of Bnda-Pest. 



