1906.] 



The Viscosity of the Blood. 



335 



After sufficient time had been allowed to elapse for the viscosiineter and 

 its contents to acquire the temperature of the bath in which it was placed, 

 the blood or other fluid content was sucked up to the point marked (m) by' 

 means of a piece of rubber tubing affixed to the capillary arm, and then 

 permitted to flow back through the bulb under the action of gravity. By 

 means of a stop watch, reading to one-fifth of a second, the time taken for 

 the end of the fluid column to flow from m" to m'" was observed. By thus 

 allowing the liquid column to get up a steady motion before observing its rate 

 of flow we eliminate to a great extent errors resulting from differences 

 of inertia of the various liquids examined. 



If t' is tbe time in seconds for water at any particular temperature, a its 

 specific gravity, whilst t is the time for the fluid examined and a its specific 

 gravity, then the relation between their viscosity coefficients 77' and 77 

 respectively is 



77 : 7f' = at : a't' , or 77 = 77'— — . Formula (II) 



a t 



The absolute value taken for the viscosity coefficient of water, that is 

 for 77', at 35° was - 007361 C.G.S. units, the value given by Thorpe and 

 Bodger. 



For those experiments in which the pressure gradient was varied the 

 narrower limb of the viscosimeter was connected to a large "Winchester bottle 

 containing compressed air, by means of a long piece of pressure tubing wired 

 on to the brass tube F.E. (vide fig. 4). Through the rubber bung in the neck 

 of the Winchester was passed a + -shaped brass union which had taps on 

 three of its arms ; one of these, C, was in communication with a force pump , 

 another, B, with a mercury manometer ; and the third, A, was connected to 

 the brass tube leading to the viscosimeter. A second brass tube, leading to 

 an exhaust (filter) pump and provided with a tap at D, was soldered 

 perpendicularly into F.E. 



Before using this accessory apparatus the tap A was closed, air was forced 

 into the Winchester until the manometer registered a convenient height, and 

 the tap C then closed. The liquid in the viscosiineter was now drawn up to 

 the topmost mark (m') by opening the tap D, and thereby connecting to the 

 filter pump. When D was closed, A was opened, and the one observer with 

 the stop-watch now noted the time of flow between the middle and lowest 

 marks on the viscosimeter tube as before, whilst the other noted the initial 

 and final pressure readings and manipulated the taps. 



2 D 2 



