Prof. TyndalFs Notes on Scientific History, 39 



titles of carbon just calculated would suffice for the times men- 

 tioned. In reality, however, besides the production of mecha- 

 nical effects, there is in the animal body a continuous genera- 

 tion of heat. The chemical force contained in the food and 

 inspired oxygen is therefore the source of two other forms of 

 power, namely, mechanical motion and heat ; and the sum of 

 these physical forces produced by an animal is the equivalent of 

 the contemporaneous chemical process. Let the quantity of 

 mechanical work performed by an animal in a given time be col- 

 lected, and converted by friction or some other means into 

 heat ; add to this the heat generated immediately in the animal 

 body in the same time, we have then the exact quantity of 

 heat corresponding to the chemical processes that have taken 

 place. 



35. In the active animal, continues Mayer, the chemical 

 changes are much greater than in the resting one. Let the 

 amount of the chemical processes accomplished in a certain time 

 in the resting animal be x, and in the active one x + y. If 

 during activity the same quantity of heat were generated as 

 during rest, the additional chemical force y would correspond to 

 the work performed. In general, however, more heat is produced 

 in the active organism than in the resting one. During work, 

 therefore, we shall have x plus a portion of y for heat, the residue 

 of y being converted into mechanical effect. 



36. I must now prove that the extra quantity of combustible 

 matter consumed by the working animal contains the necessary 

 force for the performance of the work. A strong horse, not 

 working, is amply nourished on 15 lbs. of hay and 5 lbs. of oats 

 a day. If the animal performed daily the work of lifting a weight 

 of 12,960,000 lbs. 1 foot high, it could not exist on the same nu- 

 triment. To keep it in good condition we must add 11 lbs. of 

 oats. The 20 lbs. of nutriment first mentioned is the quantity 

 which we have named x, and contains, according to Boussingault, 

 8*074 lbs. of carbon. The additional 11 lbs. of oats, our quan- 

 tity y, contains, according to the same authority, 4*734. 



According to Boussingault, also, the carbon introduced is to 

 that excreted in a combustible form as 3938 : 1364*4. Calcu- 

 lating from these data, we find x, or the quantity of carbon burnt 

 by the resting animal, 5*2766 lbs., and ?/ = 3*0941bs. The quan- 

 tity consumed in mechanical effect is 1*34 lb., which we will 

 call z. 



37. We have therefore the following relations: — 1. The 

 mechanical effect is to the total consumption as z : x + y = 0'l6. 

 2. The mechanical effect is to the surplus consumption of the 

 working animal as z : y=0*43. 3. The generation of heat at rest 

 is to the generation of heat while working as x : x -\-y— z= 0*75. 



