THE 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 
