1906.] 



The Viscosity of the Blood. 



357 



in the containing vessels may have upon the circulatory mechanism ; numerous 

 other examples might have heen added ; but for the present they will 

 sufficiently serve to indicate how the work of the heart may be relieved or 

 embarrassed by such variations. Moreover, we can thus see that the viscosity 

 of the blood is not an independent but a dependent variable, which is essential 

 for the maintenance of the series of adaptive changes that may occur in the 

 circulatory system of the individual, be they physiological or pathological. 

 And in concluding the communication we feel that the urgent need for 

 further research in this field cannot be too strongly emphasised, in so far as 

 even now we are still upon the borderland. 



Appendix I. 



Description of Clinical Viscosimeter. 



The viscosimeter which we have devised for clinical purposes consists 

 simply of a curved piece of capillary tubing with two arms. The long arm, 

 6 cm. in length, has been blown out at its free end into a cup-shaped receiver 

 with a thin edge. On the short arm, about 2 cm. in length, there is a small 

 elliptical bulb and the point at which the capillary enters and leaves the bulb 

 is etched on the glass (vide fig. 10, ml and in"). 



To use the Instrument. — The most convenient place to take the blood for 

 comparative estimations of the viscosity is, in our opinion, the lobe of the ear, 

 for not only is it less sensitive than any other part, but it can be made to 

 bleed readily without any manipulation, whilst the position of the hanging 

 drop permits the viscosimeter to be placed vertically. The lobe of the ear is 

 first well cleaned with ether and a special fine pointed knife is then inserted 

 into the most dependent part of the lobe. The viscosimeter, which has 

 previously been warmed to the temperature of the body, is now placed 

 underneath the hanging drop of blood and the receptacle filled. The moving- 

 thread of blood is carefully watched through its course clown the long limb 

 and bend of the tube, a stop-watch is held in readiness during this time and 

 the seconds finger started as soon as the column of blood reaches the point ml, 

 and stopped the moment the column gains m" . The time is now read 

 off to a fraction of a second and the result compared with the reading 

 for water. This time value is a reliable comparative indication of the 

 viscosity of the blood under examination. For it follows from Poiseuille's 

 law that if the length and diameter of the viscosimeter, the quantity of fluid, 

 and the pressure height be kept constant, and the. time be observed, then the 

 viscosity of two liquids of densities s and s" with times of flow t' and t" 

 will be as 



n' : n" — s't' : s"t" ', 



