TEE COPLEY MEDALIST OF 1871. 325 



CHAPTER XX. 



THE COPLEY MEDALIST OF 1871. 



DR. JULIUS ROBERT MAYER was educated for the med- 

 ical profession. In the summer of 1840, as he himself 

 informs us, he was at Java, and there observed that the 

 venous blood of some of his patients had a singularly 

 bright red color. The observation riveted his attention; 

 he reasoned upon it, and came to the conclusion that the 

 brightness of the color was due to the fact that a less 

 amount of oxidation sufficed to keep up the temperature 

 of the body in a hot climate than in a cold one. The 

 darkness of the venous blood he regarded as the visible 

 sign of the energy of the oxidation. 



It would be trivial to remark that accidents such as this, 

 appealing to minds prepared for them, have often led to 

 great discoveries. Mayer's attention was thereby drawn to 

 the whole question of animal heat. Lavoisier had 

 ascribed this heat to the oxidation of the food. " One 

 great principle," says Mayer, " of the physiological theory 

 of combustion, is that under all circumstances the same 

 amount of fuel yields, by its perfect combustion, the same 

 amount of heat; that this law holds good even for vital 

 processes; and that hence the living body, notwithstanding 

 all its enigmas and wonders, is incompetent to generate 

 heat out of nothing." 



But beyond the power of generating internal heat, the 

 animal organism can also generate heat outside of itself. 

 A blacksmith, for example, by hammering can heat a nail, 

 and a savage by friction can warm wood to its point of 

 ignition. Now, unless we give up the physiological axiom 

 that the living body cannot create heat out of nothing, 

 " we are driven," says Mayer, " to the conclusion that it is 

 the total heat generated within and without that is to be 

 regarded as the true calorific effect of the matter oxidized 

 in the body." 



From this, again, he inferred that the heat generated ex- 

 ternally must stand in a fixed relation to the work expended 

 in its production. For, supposing the organic processes to 

 remain the same; if it were possible, by the mere alteration 

 of the apparatus, to generate different amounts of heat by 

 the same amount of work, it would follow that the 



