458 FRAGMENTS OF SCIENCE 



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 in- 

 creased 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 cal- 

 culations. The muscles of a laborer 150 Ibs. in weight 

 weigh 64 Ibs. ; but when perfectly desiccated they fall to 

 15 Ibs. Were the oxidation corresponding to that labor- 

 er's work exerted on the muscles alone, they would be 

 utterly consumed in 80 days. The heart furnishes a still 

 more striking example. Were the oxidation necessary to 

 sustain the heart's action exerted upon its own tissue, it 

 would be utterly consumed in 8 days. And if we confine 

 oar attention to the two ventricles, their action would be 

 sufficient to consume the associated muscular tissue in 3% 

 days. Here, in his own words, emphasized in his own 

 way, is Mayer's pregnant conclusion from these calcula- 

 tions: "The muscle is only the apparatus by means of 

 which the conversion of the force is effected; but it is not 

 the substance consumed in the production of the mechanical 

 effect." He calls the blood "the oil of the lamp of life"; 

 it is the slow-burning fluid whose chemical force, in the 

 furnace of the capillaries, is sacrificed to produce animal 

 motion. This was Mayer's conclusion twenty-six years 

 ago. It was in complete opposition to the scientific con- 

 clusions of his time; but eminent investigators have since 

 amply verified it. 



