150 SANGUIFICATION. L.ECT. VII. 



and water, absorbed, Dulong, and afterwards Despretz, 

 found that for every 100 parts of heat produced by the 

 animal, and received by the calorimeter, 80 or 90 only 

 were produced by the combustion of the carbon and hy- 

 drogen, calculating from the carbonic acid and water 

 evolved by the animal. 



If we reflect that the temperature of an animal placed in 

 a calorimeter, is always higher than that of the surrounding 

 water, and that the animal is in consequence cooled during 

 the experiment, we find, in the fact of this refrigeration, a 

 plausible explanation of the excess of caloric met with. 

 And, indeed, the numerous experiments of Despretz have 

 clearly proved that the excess of heat received by a calori- 

 meter over that which is due to respiratory combustion, is 

 greater in proportion as the animal is. younger and its tem- 

 perature higher. We know, moreover, from the beautiful 

 experiments of Edwards, that young animals cool much 

 more rapidly than adults. 



These considerations are sufficient to show that the excess 

 met with in the calorimeter can be explained, without 

 having recourse to any special power, to a vital property 

 which engenders heat. 



I must also add, that after the death of the celebrated 

 Dulong, there was found in his unpublished papers an 

 account of several other experiments relating to the heat 

 developed by the combustion of hydrogen. This heat 

 should be much more considerable than that which was 

 first found by Dulong and Despretz. The numbers fixed 

 by the later experiments of Dulong have since been con- 

 firmed by those of Fabre and Silberman. Now, in adopt- 

 ing this new number, we no longer find an excess of heat 

 yielded to the calorimeter over that developed by the com- 

 bustion of hydrogen and carbon, but on the contrary, a 

 deficiency. 



