HEALTH AND THE LAWS OF MECHANICS 133 



White rats are also indisposed to this same 

 infection ; but subjecting them to fatigue, these 

 little animals lose their immunity. Charron and 

 Roger placed them in special cages, which obliged 

 the rats experimented upon to be always moving, 

 with the result that these little animals became 

 victims, like the previous ones, to the carbuncular 

 bacteria. 



From these examples I think we can understand 

 the relation health maintains with the general 

 principles of mechanics, more especially with one 

 of the thermo-chemical laws of Berthelot : The 

 amount of heat that is released in any reaction is 

 the measure of the sum of the physical and chemical 

 labour produced by it. Thus stated, the problem 

 seems to us far clearer and simpler, and more in 

 harmony with the spirit of modern biological science, 

 which can admit no other laws than the general 

 laws of mechanics. The hen in its normal state 

 represents a chemical combination, definite and 

 concrete, that admits of no disintegration on the 

 part of the infectious agent ; in making the said 

 bird lose its normal temperature one causes it to 

 lose a great amount of heat. Well, then, according 

 to the law of equilibrium of forces, this amount of 

 heat lost by the hen presupposes an equal loss in 

 chemical and electrical affinity, etc., and indeed 

 we may say even in radio-activity. As all these 



