332 



Dr. A. du Pre Denning and Mr. J. H. Watson. [May 7, 



After we had commenced the experiments described in this paper, we 

 learnt that Dr. E. J. Ewart, of Manchester, had been working at the same 

 subject for some time. At our request he very kindly indicated to us the 

 particular lines of investigation he had pursued. By a very ingenious 

 though complex apparatus he found that the average value for the viscosity 

 of defibrinated pig's blood with a capillary of 043 mm. radius is 3'8 times 

 that of water, whereas that of dog's blood is 4*1, cat's, 4 - 2 ; whilst that of 

 man is 3 "14. 



Further, he has carried out experiments on animals asphyxiated with excess 

 of CO and C0 2 , and found a rise in the viscosity. He also observed the 

 result of substituting - 6 per cent, saline for pig's serum, and confirmed the 

 fact that an increase in the number of corpuscles in the blood resulted in an 

 increase in the value of the viscosity coefficient. 



Furthermore, he states that the viscosity coefficient of blood flowing 

 through capillary tubes did not vary as the fourth power of the radius, as 

 required by Poiseuille's law.* 



Description of Apparatus. 

 The present experiments were undertaken in the first place to observe : — 



(a) The influence of the number of corpuscles present upon the viscosity 



of the blood under varying conditions of temperature and pressure ; 



(b) The effect of the size of different capillary bores upon the rate of flow, 



again varying the number of corpuscles, temperature and pressure ; 



(c) The alterations, if any, caused by the addition of certain salts and other 



substances ; 

 and, ultimately, 



(d) To devise a viscosimeter for clinical purposes which would give reliable 



results with a very small quantity of blood. 



A general idea of the actual arrangement of the various parts of the 

 apparatus employed is most easily obtained from the photographic represen- 

 tation given in fig. 1 (a and b). 



In order to study the effect of temperature, four thermostats were main- 

 tained at temperatures of approximately 32° C, 36° C, 40° C, and 44° C. 

 respectively. Each thermostat consisted of a large glass beaker, of about 

 2 litres capacity, containing (a) a toluene-mercury gas regulator; (b) a 

 thermometer ; (c) a pear-shaped glass stirrer driven, in series with the other 

 three stirrers, by a small electric motor, shown to the right of the 

 photograph. 



* Ewart, ' Thesis for D.Sc, Liverpool,' 1904. 



