82 PHYSIOLOGY OF MUSCLES AND NERVES. 



to perform a great amount of labour require food 

 aboundiug in carbon. The opposite was formerly as- 

 sumed, the view being founded on the fact that English 

 labourers, who are, as a rule, more capable of work 

 than French peasants, eat more meat, which is a highly 

 nitrogenous substance. It used also to be pointed out 

 that the larger beasts of prey, which feed exclusively 

 on flesh, are remarkable for their great muscular power. 

 Neither instance really proves the conclusion which it 

 was intended should be drawn from it. In the first 

 place, as regards English labourers, more accurate ob- 

 servation of the food usually consumed by them has 

 shown that, in addition to meat, very considerable 

 quantities of food abounding in carbon, such as bread, 

 potatoes, rice, and so on, are taken. As regards the 

 beasts of prey, it is impossible to deny that they are 

 capable of very great labour; but in this case, also, 

 closer observation shows that the whole amount of 

 work accomplished by them is, at any rate, very small 

 when compared with the constant work of a draught 

 horse or ox. 



The relation of the food to the work performed by 

 the muscles must evidently be regarded as similar to 

 the relation borne by the fuel consumed by an engine 

 boiler to the work performed by a steam-engine. Every- 

 one knows that coal is burned under the boiler, and 

 that this is finally transformed into work by the me- 

 chanism of the machine. The same work might be 

 produced by the combustion of nitrogenous matter ; 

 but it would be necessary to use considerably greater 

 quantities. But the machine called muscle cannot be 

 driven by pure carbon ; under the conditions presented 

 by the organism pure carbon cannot be applied to the 



