ON THE SOURCE OP MUSCULAR POWER. 253 



kilogram weight to the height of one metre. The researches of Joule 

 and Mayer have comiected this standard unit with heat ; — they prove 

 that the force required to elevate this weight 425 times will, when 

 converted into heat, raise the temperature of an equal weight of water 

 1° C. If this weight were let fail from a height of 425 metres, its 

 collision with the earth would produce an amount of heat sufficient 

 to raise the temperature of 1 kilogram of water 1° C. The same 

 heating eifect would also of course be produced by the fall of 425 

 kilograms through 1 metre. This standard of force is termed a me- 

 trekilogram ; * and 425 metrekilograms are equal to that amount of 

 heat which is necessary to raise the temperature of 1 kilogram of 

 water through 1*^ C. If then it be found that the heat evolved by 

 the combustion of a certain weight of charcoal or muscle, for in- 

 stance, raises the temperature of 1 kilogram of water through 1° C, 

 this means, when translated into mechanical power, 425 metrekilo- 

 grams. Again, if a man weighing G4 kilograms climbs to a height 

 of 1,000 metres, the ascent of his body to this height represents 

 64,000 metrekilograms of work ; that is, the labour necessary to raise 

 a kilogram weight to the height of 1 metre 64,000 times. 



The author then proceeds to describe the manner in which he de- 

 termined the actual energy developed by one gram of each the sub- 

 stance in the following list, when burnt in oxygen : — 



Beef Muscle 2,1611 



Albumin 2,117 { 



Beef Fat 3,841 [Metrekilograms 



Hippuric Acid 2,280.' of Force. 



Uric Acid 1,108 { 



Uria..... 934J 



The heat evolved was determined by means of a calorimeter of pe- 

 culiar construction ; the substance being burnt by means of chlorate 

 of potassa, and various corrections introduced. 



It is evident that the above determination of the actual energy 

 developed by the combustion of muscle in oxygen represents more 

 than the amount of actual energy produced by the oxidation of 

 muscle within the body, because, when muscle hums in oxygen its 

 carbon is converted into carbonic acid, and its hydrogen into water ; 

 the nitrogen being, to a great extent, evolved in the elementary state ; 



* I follow the example of the Registrar-General in abbreviating the French 

 word gramme to gram. 



