114 Chapter VII 



The comparative viscosity of the solutions used was determined by 

 measuring the time of flow of a given quantity through a tube of small 

 bore. The apparatus used was kindly lent by Mr W. B. Hardy. It con- 

 sisted of a capillary tube and arrangements for causing flow at constant 

 temperature and under constant pressure. At a temperature of 37 C. 

 and pressure of 37 mm. of water, the results were as follow : 



Comparative viscosity from average time of flow. 



Distilled water 1 min. 5 sec. 



Gum acacia (5 / ) in saline ... ... 2 ,, 22 ,, 



Defibrinated blood ... ... ... ... 5 ,, 



Gelatine (5 / ) in saline ... ... ... 6 ,, 



Soluble starch (3 / ) in saline 10 ,, 20 ,, 



It is clear therefore that the efficiency of starch, gum acacia 

 and gelatine in counteracting the effect of the Ringer's solution is 

 in proportion to their osmotic pressures and not in proportion to 

 their viscosities. Nor can this effect be attributed to changes in the 

 rate of flow of blood through the kidney, to the general arterial 

 pressure or to the activity of the cells. 



But if further proof of the mechanical nature of Ringer diuresis 

 be needed it may be found in the fact that these characteristic 

 actions of gelatine and starch can only be obtained on those forms of 

 diuresis which are unaccompanied by a call for oxygen. Salt solution 

 seems frequently to act in just the same way ; in such cases what we 

 have just said about Ringer's solution might with equal truth have 

 been said of a solution of sodium chloride. Sometimes however 

 sodium chloride may cause a secretion by the tubules as well as 

 its mechanical diuresis. 



We have already shown that diuresis obtained by sodium sulphate 

 is not of this character. There is increased work done by the kidney 

 as evidenced both by the call for oxygen and by the fact that the urine 

 is, or may be, almost a pure solution of sodium sulphate. 



The presence of gelatine in the sodium sulphate solution injected 

 does not counteract the action of the sodium sulphate or at least it 

 does so only to a trifling extent, for although sodium sulphate has a 

 specific secretory action it must of course have a salt action as well. 



The information which has been recounted in the preceding pages 

 appeared to be in conflict with a statement which is often put 

 forward as being one of the fundamental facts with regard to urinary 

 secretion, namely that a kidney, the artery of which has been clamped, 

 does not secrete urine for a long time. Winfield and I determined 



