398 THE MECHANICS OF THE CIRCULATION, HEMODYNAMICS 



only a fraction of a degree above that of the water in which the parts were immersed. 

 The flow is calculated in grammes per minute in accordance with the formula : 



Q 



H 



1 



M{T - T') S 



Q being the quantity of blood, H the number of small calories given off in Af 

 minutes, T the temperature of the entering blood, T' the temperature of the out- 

 flowing blood, and S the specific heat of the blood. The volume of the hands or 



Fig. 210. — Kidney Oncometer. 

 I, the kidney is placed into the oncometer consisting of two hemispherical parts, 

 connected with a recording tambour (T). II, the sides of this oncometer are lined with 

 rubber membrane, the space between the membrane and the metal wall being filled with 

 water of 37° C. The upper bag is connected with a recording tambour. 



feet is measured by permitting them to displace an equal quantity of water from a 

 graduated receptacle. The bloodflow is expressed in grammes per 100 c.c. of 

 tissue per minute. 



These tests upon the hands of normal individuals have given the average value 

 of 5.5 grammes of blood per 100 c.c. of hand- volume in a minute, but naturally, 

 this figure is subject to considerable variations, because the vascularity of a part 

 may be changed at any time either by influences brought to bear upon it directly, or, 



Fig. 211. — Diagram of Schafbe's Air Plethysmograph (Spuenic Oncometer). 

 P, box for insertion of spleen; R, piston-recorder; L, writing lever. 



in an indirect way, by reactions occurring in other regions of the body. In a robust 

 young man the average flow amounted to 12.8 grammes per 100 c.c. of hand per 

 minute for the right hand and to 12.3 grammes for the left. In the foot, the 

 flow per unit of volume of the part is smaller than in the hand. In the forearm the 

 flow is much less than in the hand (Hewlett). 



The blood supply of an organ may also be determined in an approximate way 



