1906.] 



The Viscosity of the Blood. 



343 



the corpuscles in the blood does not seriously affect the application of 

 Poiseuille's law to it as a fluid." 



From the results of some of his experiments, Dr. Ewart has arrived at 

 the rather astonishing result that a blood containing 5 - 10 G corpuscles per 

 cubic millimetre requires least expenditure of energy on the part of the 

 heart to drive a definite quantity of it in unit time past any particular 

 cross-section, or, as he says, human blood containing five million corpuscles 

 per cubic millimetre is mechanically the most efficient and economical. 

 Similar calculations from our observations, however, have not afforded the 

 slightest confirmation of such an unexpected result. Nor do Dr. Ewart's 

 own results always agree with it. 



It would, moreover, appear to us that the deduction is by no means 

 justifiable or, indeed, valid, inasmuch as the calculations rest upon direct 

 comparison between three different kinds of blood, viz., pig's blood for the 

 value with the 6 - 10 6 corpuscles, human blood for that with 5 - 10 6 , and a 

 mixture of human and pig's serum for the lower values. As will be seen 

 later, the mere number of corpuscles present is far from being the only factor 

 which may influence the viscosity of a blood. 



The Effect of Change of Temperature. — At the bottom of each sub-section 

 is given the change in viscosity which resulted from a change of temperature 

 of 1° C, that is, the mean temperature coefficient at temperatures of about 

 blood heat. And if we take any one series, it is apparent that this tem- 

 perature coefficient increased with increase in the number of corpuscles. 

 In figs. 7 and 8 are plotted the values of the viscosity coefficient found at 

 different temperatures for the three series, Table II (B), and Table III (A) 



45°C. 



£40° 

 s_ 



3 



■a 



30° 







\ \ 



V 







M 



iD\ 

 <£\ 

 -J\ 

 °-A 



A 

 +\ 



**\ 



\ 



+ \ 



<p\ 









V 



\ 





•015 



•020 -025 



Viscosity Coefficients 



•035 



Fig. 7. — Curves showing Temperature Effect with varying number of Corpuscles. 



(Cf. Table II [B].) 



