XX. 



THE COPLEY MEDALIST OF 187L 



DR. JULIUS EGBERT MAYER was educated for 

 the medical 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 colour. The observation 

 riveted his attention ; he reasoned upon it, and came to 

 the conclusion that the brightness of the colour 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 combus- 

 tion, 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 incom- 

 petent to generate heat out of nothing.' 



But beyond the power of generating internal heat, 



