ON HEAT GENERATED IN THE BLOOD. 



231 



been deteiinincd by Dr. John Davy alone, his experiments being recorded in 

 his previously quoted work (vol. p. 141), in a chapter entitled " On the Capa- 

 cities of Venous and Arterial Blood for Heat." In his experiments he made 

 use of defibriiiated blood, and employed for the determination of specific heat 

 the methods of mixture and rate of cooling. According to Da-vy, the specific 

 heat of lambs' and sheeps' blood varied from 0-812 to 0-934 (water beini? 

 1-0). 



The great discrepancy of these results made it most desirable that the 

 determination should now be made in an accurate manner. 



I employed invariably the method of mixture. 



A flask furnished with a tubulaturc near its base was fixed in the centre 

 of a water-bath, and from the flask a tube, also surrounded by hot water, 

 proceeded, which communicated with the exterior by means of a stopcock. 

 This flask was filled with mercury. The blood to be experimented upon was 

 placed in a light and highly poUshed iron vessel, which was surrounded by 

 cotton-wool, and placed in a glass beaker. The temperature of the blood 

 and mercury was ascertained before and after mixture by means of a very 

 delicate standard thermometer, made by Fastre of Paris, belonging to the 

 Museum of Natural Philosophy of the University of Edinburgh. This ther- 

 mometer admitted of being read very accurately to fiftieths of a degree 

 Centigrade. 



In my experiment, heated mercury was added to blood at a lower tem- 

 perature. 



The specific heat was determined by the usual formula. 



C specific heat of blood. 



M weight of blood. 



T its temperature. 



m weight of mercury. 



t its temperature. 



c' its specific heat, i. e. 0-033. 



d temperature of mixture of blood and mercury. 



fi specific heat of vessel. 



f,_ m(t—d)c' 



(M+^0(e-T)" 



The results of my experiments, which were all performed with perfectly 

 fresh ox's blood, are exhibited below in a tabular form : — 



The above determinations were aU made with the perfectly fresh blood of 

 the ox ; and they may, I think, be considered as representing very accurately 

 the specific heat of blood. 



They show that the specific heat of blood is not, as Davy supposed, con- 



