LECT. VII. ANIMAL HEAT. 149 



transformation of tissues, and especially in the combination 

 of oxygen with carbon.* 



I have no wish, nor, indeed, am I able, to describe any 

 other hypothesis relating to the sources of animal heat. 

 When, in consequence of dividing the pneumo-gastric 

 nerves, or the spinal marrow, we find, by a thermometer 

 placed in the tissues of the animal, that the temperature 

 falls, and from this conclude that innervatlon was the direct 

 cause of animal heat, we do not consider that respiration 

 and the circulation of the blood have been diminished in 

 consequence of the division of the nerves and spinal cord. 

 Instead of discussing hypotheses like these, it is preferable 

 to examine more deeply, and in detail, the chemical ac- 

 tions which we consider to be the sole source of animal 

 heat. 



Natural philosophers are anxious to prove the truth of 

 these hypotheses. An animal exhales, in a given time, a 

 certain quantity of carbonic acid and water, and simultane- 

 ously developes a quantity of heat, which may be measured 

 by the quantity of water which it is capable of heating in 

 the same space of time. If the carbonic acid and the 

 water, which the animal exhales, be the products of the 

 combustion of carbon and of hydrogen, the heat given out 

 by the animal ought, these philosophers say, to be equal to 

 that which the same quantities of carbon and hydrogen 

 produce when burnt in the air. 



By setting out with the data furnished by a calorimeter, 

 in which the animal was placed, noting the temperature 

 acquired by the water, and measuring, at the same time, 

 the oxygen which the animal or its products, carbonic acid 



* If Dr. G. O. Rees's theory of respiration be correct (see foot-note at 

 p. 141,) the oxidation of phosphorus, contained in the venous corpuscles, 

 must be one source of animal heat. J. P. 



