515 



For this purpose, the vessel which serves as condensing worm-tub 

 to the first distillation requires to be fitted with a head and a receiver, 

 all perfectly air-tight ; and it may with most convenience be so con- 

 structed, that, by application of heat in the first instance to this ves- 

 sel, the water within may be made to boil completely, so that the air 

 within it will be thereby expelled, and, by a valve or cock, may be 

 prevented from returning when the heat is withdrawn. 



An Account of some Experiments on Animal Heat. By John Davy, 

 M.D. F.R.S. Read February 17, 1814. [Phil. Trans. 1814, 

 p. 590.] 



The experiments here detailed relate, in the first place, to the rela- 

 tive capacities of venous and arterial blood for heat ; secondly, the 

 comparative temperature of these fluids in different parts of the body 

 during life is attempted to be ascertained ; and thirdly, the author 

 states those conclusions which he thinks may be drawn from his ex- 

 periments. 



In his first experiments he endeavours to discover the relative ca- 

 pacities by the times of cooling equal volumes of venous and arterial 

 blood, regard being also had to the specific gravities of each. When 

 blood was taken from the jugular vein of a lamb, and after the fibrin 

 had been separated from it by stirring with a wooden spatula, its 

 specific gravity was found to be 1050, that of arterial blood from the 

 same lamb, similarly treated, being 1047. The quantity of each 

 taken for experiment was the same, contained in the same vessel, 

 and heated to the same degree. An equal quantity of water in this 

 vessel had cooled from 1 20 to 80 in ninety-one minutes ; arterial 

 blood cooled, through the same interval, in eighty-nine minutes ; and 

 venous blood in eighty- eight minutes : and hence the author infers 

 the capacity of venous blood to be to that of arterial as 92 to 93 '7, 

 that of water being 100. By other experiments made on various 

 mixtures of these fluids with each other at different temperatures, he 

 estimates the proportion to be 93 to 9'3'7. 



In subsequent trials on the rates of cooling observed in blood that 

 still contained its fibrin, Dr. Davy estimated the capacities of venous 

 and arterial blood to be as 90 to 91. 



The next experiments were upon the proportional heat lost in a 

 given time by mixtures of either kind of blood with water, due allow- 

 ance being made, as before, for the difference of their specific gravi- 

 ties (viz. 1050 and 1049). 



In this mode of trial the proportions were nearly reversed, the ca- 

 pacity of venous blood appearing to be 95*4, whilst that of arterial 

 was no more than 94' 8. But the author observes, that these trials 

 admit of less accuracy than the preceding ; and he would be inclined 

 to consider the third set of experiments as most entitled to confidence. 



Dr. Davy's first experiments on the actual temperatures of venous 

 and arterial blood in the living body, were made at the great vessels 

 of the neck in lambs, sheep, and oxen ; and in each a difference was 

 2 L2 



