CHAP. XXX.J THEORY OF ANIMAL HEAT. 427 



To explain the prompt oxidation of the carbon and hydrogen 

 within the body, Liebig has pointed out that the oxygen is pre- 

 sented to them not in a gaseous but in a liquid or solid form that 

 in the innumerable channels of the circulation, these several ele- 

 ments are not merely brought together in a very subdivided state, 

 but everywhere in close proximity to membranous surfaces, me- 

 chanically adapted to favour the occurrence of chemical union. 

 Moreover, that the carbon and hydrogen are not offered to the 

 oxygen in their pure and simple state, but in combinations already 

 existing and ready to be dissolved. He also insists, with great 

 force, on the analogy of these actions to those promoted by the 

 presence of a body already undergoing oxidation. For example, 

 " when weak brandy is allowed to trickle over shavings in a closed 

 vessel, through which a feeble current of air at from 93 to 97 F. 

 circulates, the alcohol in the brandy remains unchanged ; in spite 

 of the greatly increased surface, no oxidation, no formation of 

 acetic acid takes place. But if to the brandy there be added one 

 hundred thousandth part of vinegar, beer, or wine, in the state of 

 acetification, that is, of oxidation, the alcohol disappears with 

 great rapidity, and is converted by the absorption of oxygen, into 

 an equivalent quantity of acetic acid. In the vessel the surface 

 of the shavings themselves very soon passes into the state of oxi- 

 dation, and from this period forth, the brandy is acetified without 

 the addition of a ferment : the wood, being in the state of decay, 

 eremacausis, or slow combustion, plays the part of a ferment. 

 These vinegar-producing vats give an idea, if only a rough one, 

 of the process of oxidation going on in the animal body. As in 

 the body, so also in these vessels, a temperature higher than that 

 of the surrounding media is kept up, without the aid of external 

 heat." * 



These actions of contact or catalysis may well be supposed to 

 play a large and most important part, not merely in the production 

 of animal heat, but also in all the chemical changes which are 

 ever going on in the body, from the first reception of food to the 

 final expulsion of its elements in other forms of combination. 

 Great obscurity, however, still hangs over the series of transforma- 

 tions which the food undergoes in its passage through the body. 



It has been seen that both arterial and venous blood contain 

 oxygen and carbonic acid gas in a state of solution ; but into what 

 form of combination the oxygen first enters, or from what imme- 

 diate source the carbonic acid is derived, is as yet matter of con- 

 * '< Animal Chemistry," p. 34, 3rd edition, Part I. 



F F 2 



