-1859] WRITINGS OF JOSEPH HENRY. 127 



Hence oxygen is constantly drawn into the lungs, and car- 

 bon is constantly evolved. In the adult animal when a 

 dynamic equilibrium has been attained the nourishment 

 which is absorbed into the system is entirely expended in 

 I^roducing the power to carry on the various functions of life, 

 and to supply the energy necessary to perform all the acts 

 pertaining to a living, sentient, and it may be, thinking be- 

 ing. In this case, as in that of the plant, the power may be 

 traced back to the original impulse from the sun, which is 

 retained through a second stage, and finally given back 

 again to celestial space, whence it emanated. All animals 

 are constantly radiating heat, though in different degrees, 

 the amount in all cases being in proportion to the oxygen 

 inhaled and the carbon exhaled. The animal is a curiously 

 contrived arrangement for burning carbon and hydrogen, 

 and the evolution and application of power. In this respect 

 it is precisely analogous to the locomotive, the carbon burnt 

 in the food and in the wood performing the same office in 

 each. The fact has long been established that power cannot 

 be generated by any combination of machiner3^ ^ machine 

 is an instrument for the application of power, and not for 

 its creation. The animal body is a structure of this char- 

 acter. It is admirably contrived, when we consider all the 

 offices it has to perform, for the purpose to which it is 

 applied, but it can do nothing without power, and that, as 

 in the case of the locomotive, must be supplied from with- 

 out. Nay more, a comparison has been made between the 

 work which can be done by burning a given amount of car- 

 bon in the machine, man, and an equal amount in the ma- 

 chine, locomotive. The result derived from an analysis of 

 the food in one case and the weight of the fuel in the other, 

 and these compared with the quantity of water raised by 

 each to a known elevation, gives the relative working value 

 of the two machines. From this comparison, made from 

 experiments on soldiers in Germany and France, it is found 

 that the human machine, in consuming the same amount 

 of carbon, does four and a half times the amount of work of 

 the best Cornish engine. The body has been called " the 



