XX. 



TEE COPLEY MEDALIST OF 1871. 



DR. JULIUS ROBERT 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 ob- 

 servation 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 oxida- 

 tion 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 

 incompetent to generate heat out of nothing.' 



But beyond the power of generating internal heat, 

 428 



