Animated Creatures over Matter. 259 



work ; by which it appears that probably as much as ^ of the 

 whole work of the chemical forces arising from the oxidation of 

 his food during the twenty-four houi's, may be directed to raising 

 his own weight, by a man walking up-hill for eight hours a day ; 

 and perhaps even as much as ^ of the work of the chemical forces 

 may be directed to the overcoming of external resistances by a 

 man exerting himself for six hours a day in such operations as 

 pumping. In the former case thei'e would not be more than ^, 

 and in the latter not more than f of the thermal equivalent of 

 the chemical action emitted as animal heat, on the whole, dming 

 the twenty-four hours, and the quantities of heat emitted during 

 the times of working would bear much smaller proportions re- 

 spectively than these, to the thermal equivalents of the chemical 

 forces actually operating during those times. 



A curious inference is pointed out, that an animal would be 

 sensibly less warm in going up-hill than in going down-hill, were 

 the breathing not greater in the former case than in the latter. 



The application of Carnot^s principle, and of Joule's discoveries 

 regarding the heat of electrolysis and the calorific effects of mag- 

 neto-electricity, is pointed out; according to which it appears 

 nearly certain that, when an animal works against resisting force, 

 there is not a conversion of heat into external mechanical effect, 

 but the full thermal equivalent of the chemical forces is never 

 produced ; in other words, that the animal body does not act as a 

 thermo -dynamic engine ; and very probable that the chemical forces 

 produce the external mechanical effects through electrical means. 



Certainty regarding the means in the animal body by which 

 external mechanical effects are produced from chemical forces 

 acting internally, cannot be arrived at without more experiment 

 and observation than has yet been applied ; but the relation of 

 mechanical equivalence, between the work done by the chemical 

 forces, and the final mechanical effects produced, whether solely 

 heat, or partly heat and partly resistance overcome, may be as- 

 serted with confidence. Whatever be the nature of these means, 

 consciousness teaches every individual that they are, to some ex- 

 tent, subject to the direction of his will. It appears, therefore, 

 that animated creatures have the power of immediately applying, 

 to certain moving particles of matter within their bodies, forces 

 by which the motions of these particles are directed to produce 

 desired mechanical effects. 



On the Sources available to Man for the production of Mechanical 



Effect. 



Men can obtain mechanical effect for their own purposes either 

 by working mechanically themselves, and directing other animals 

 to work for them, or by using natural heat, the gravitation of 

 descending solid masses, the natural motions of water and air, 



S2 



