THE COPLEY MEDALIST OF 1871. 435 



' I count,' he says, ' therefore, upon your agreement with 

 me when I state, as an axiomatic truth, that during 

 vital processes the conversion only, and never the 

 creation of matter or force occurs.' 



Having cleared his way through the vegetable world, 

 as he had previously done through inorganic nature, 

 Mayer passes on to the other organic kingdom. The 

 physical forces collected by plants become the property 

 of animals. Animals consume vegetables, and cause 

 them to reunite with the atmospheric oxygen. Animal 

 heat is thus produced ; and not only animal heat, but 

 animal motion. There is no indistinctness about Mayer 

 here; he grasps his subject in all its details, and reduces 

 to figures the concomitants of muscular action. A 

 bowler who imparts to an 8-lb. ball a velocity of 30 feet, 

 consumes in the act -^ of a grain of carbon. A man 

 weighing 150 Ibs., who lifts his own body to a height 

 of 8 feet, consumes in the act 1 grain of carbon. In 

 climbing a mountain 10,000 feet high, the consumption 

 of the same man would be 2 oz. 4 drs. 50 grs. of carbon. 

 Boussingault had determined experimentally the ad- 

 dition to be made to the food of horses when actively 

 working, and Liebig had determined the addition to be 

 made to the food of men. Employing the mechanical 

 equivalent of heat, which he had previously calculated, 

 Mayer proves the additional food to be amply sufficient 

 to cover the increased oxidation. 



But he does not content himself with showing, in a 

 general way, that the human body burns according to 

 definite laws, when it performs mechanical work. He 

 seeks to determine the particular portion of the body 

 consumed, and in doing so executes some noteworthy 

 calculations. The muscles of a labourer 150 Ibs. in 

 weight weigh 64 Ibs. ; but when perfectly desiccated they 

 fall to 15 Ibs, Were the oxidation corresponding to 



