1906.] The Viscosity of the Blood. 349 



Table VI. — Giving Comparative Values between a Wide Tube and a 



Capillary. 



Bore. 



3 *5 mm. 



'6 mm. 



Temperature; 



Plasma. 



Plasma + 16-10" corpuscles per cub. millim. 



n- 



R. 



■o- 



E. 



V- 



E. 



C. 

 32 -2 

 45 -0 

 18 -2 



-0091 

 -0086 



1-24 

 1-17 



-0386 

 -0288 

 -0745 



5 3 

 3 9 

 10 -2 



0-208 

 0-541 



28 -4 

 74-0 



35° C. with the big tube, but 28 - 4 with the smaller, whilst determinations 

 made at the atmospheric temperature, viz., 18°"2 C, gave values of 10-2 and 

 74 respectively, showing the absolute futility of taking measurements of 

 viscous blood without simultaneously recording the temperature and the 

 approximate bore of the narrow portion of the viscosimeter, for example, as 

 Dr. F. Parkes Weber* has neglected to do. 



The Effect of Change of Pressure. — -The results of a series of experiments 

 carried out with the accessory apparatus, shown in fig. 4, are given in 

 Table VII. The pressure range adopted lay between 17'6 cm. Hg and 

 2 - 2 cm., or was somewhat larger than that generally met with in the human 

 system. The corrected values for the pressures, that is to say, the readings 

 of the manometer and a correction for the difference of level of the blood in 

 the viscosimeter tubes, are tabulated in the first column of each sub-section, 

 the outflow time in seconds in the second column, and the calculated values 

 of t] in absolute units in the third. Obviously if the different specimens of 

 blood obeyed Poiseuille's law for these changes of pressure the product 

 " pressure x time " should be a constant, that is, the calculated values 

 for r, should be constant. For the result recorded in the first two sub- 

 sections this will be seen to hold within the limits of experimental error. 



But for the blood containing 6-10 6 corpuscles per cubic millimetre, and 

 more especially for that 9 - 6 x 10 6 in a tube of 3 mm. diameter, it is evident 

 that a gradual decrease of pressure resulted in a gradual increase in the tj. 

 Or with a fine capillary (e.g., animal capillaries) the time of outflow is not 

 simply inversely proportional to the pressure as required by the Poiseuille 

 formula. With tubes of wider bore, and over the same range of pressure 

 and number of corpuscles, such marked deviations were not detectable. 



* 'Clinical Society's Transactions,' 1904. 



VOL. LXXVIII. — B. 



