ANIMAL HEAT. 



21 



whicli go up the cliimney. These products must be elimi- 

 nated. Again, tho, circulation undertakes this office ; the 

 blood dissolves the carbonic acid and the salts which are the 

 ultimate products of organic oxidation, and then carries 

 them, in its perpetual course, to the eliminating organs, the 

 lungs and the glands. 



So long as it remained unsuspected that heat and mechanical 

 work could be substituted for each other, an attempt was 

 made to account for all the combustions which take place 

 in the living organism, by estimating the quantity of heat 

 discharged by an animal in a given time. Physicists and 

 physiologists made great efforts to determine this illusory 

 equality between the theoretical heat, which corresponded 

 with the combustions which take place in the organism, and 

 the quantity of heat furnished by the animal under experi- 

 ment. 



Just as a machine, when it is working, furnishes less heat 

 to the calorimeter than would be given out by a simple grate 

 consuming the same quantity of combustible matter, so the 

 living being gives out less heat in proportion as it executes 

 more mechanical work. We have seen, by Hirn's experiments, 

 that it is solely according to the difference which exists 

 between the heat experimentally obtained and that theo- 

 retically estimated, that we now endeavour to find the value 

 of the equivalent of mechanical work in living beings. 



Whatever may be the varied manifestations of force in the 

 organism, a certain portion of that force always appears 

 under the form of heat, and this it is which gives to animals 

 a higher temperature than that of the medium in which they 

 live. 



May we not, by ascertaining the temperature of the different 

 parts of the body of the animal, discover the points at which 

 heat is formed, and define the actual seat of those com- 

 bustions of which we establish only the distant results ? 



It is now demonstrated that the lungs, by which the oxygen 

 of the air penetrates into the organism, are not the seat of 

 combustion, because the blood which comes out of that organ 

 is, in general, colder than that which has gone into it. If 

 two thermometers or thermometrical needles be introduced 



