THE COPLEY MEDALIST OF 1871. 435 



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 that labourer'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 our attention to the two 

 ventricles, their action would be sufficient to consume 

 the associated muscular tissue in 3 days. Here, in his 

 own words, emphasised in his own way, is Mayer's 

 pregnant conclusion from these calculations: * 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 conclusions of his time; but eminent investi- 

 gators have since amply verified it. 



Thus, in baldest outline, I have sought to give some 

 notion of the first half of this marvellous essay. The 

 second half is so exclusively physiological that I do 

 not wish to meddle with it. I will only add the illus- 

 tration employed by Mayer to explain the action of 

 the nerves upon the muscles. As an engineer, by the 

 motion of his finger in opening a valve or loosing a 

 detent, can liberate an amount of mechanical motion 

 almost infinite compared with its exciting cause, so 



