380 FKAGMENTS OF SCIENCE. 



drawn from the sun. A man weighing 150 pounds has 

 64 pounds of muscle; but these, when dried, reduce 

 themselves to 15 pounds. Doing an ordinary day's 

 work, for eighty days, this mass of muscle would be 

 wholly oxidised. Special organs which do more work 

 would be more quickly consumed: the heart, for ex- 

 ample, if entirely unsustained, would be oxidised in 

 about a week. Take the amount of heat due to the 

 direct oxidation of a given weight of food; less heat 

 is developed by the oxidation of the same amount of 

 food in the working animal frame, and the missing 

 quantity is the equivalent of the mechanical work ac- 

 complished by the muscles. 



I might extend these considerations; the work, 

 indeed, is done to my hand but I am warned that 

 you have been already kept too long. To whom then 

 are we indebted for the most striking generalisations 

 of this evening's discourse? They are the work of 

 a man of whom you have scarcely ever heard the 

 published labours of a German doctor, named Mayer. 

 Without external stimulus, and pursuing his profes- 

 sion as town physician in Heilbronn, this man was the 

 first to raise the conception of the interaction of heat 

 and other natural forces to clearness in his own mind. 

 And yet he is scarcely ever heard of, and even to scien- 

 tific men his merits are but partially known. Led by 

 his own beautiful researches, and quite independent 

 of Mayer, Mr. Joule published in 1843 his first paper 

 on the ' Mechanical Value of Heat; ' but in 1842 Mayer 

 had actually calculated the mechanical equivalent of 

 heat from data which only a man of the rarest pene- 

 tration could turn to account. In 1845 he published 

 his memoir on ' Organic Motion,' and applied the 

 mechanical theory of heat in the most fearless and pre- 

 cise manner to vital processes. He also embraced the 



