502 PHYSIOLOGY AT THE FARM. 



statement is, that about 25 grains per pound weight of the 

 human body, under moderate exertion, is the average daily 

 quantity thrown out by the lungs, and " if 3 grains be added 

 to this for the waste-matter of the bowel, the total will be 

 about 28 grains for each pound of the body's weight daily." 

 He takes the weight of a man at 150 pounds, and states that 

 the actual quantity of carbon contained in the food of English 

 workpeople, according to the severity of the exertion, is from 

 30 to 38 grains per pound of body-weight. 



Thus, according to Dr Smith's observations, the amount of 

 carbon available for the evolution of carbonic acid gas by the 

 lungs in working people is nearly from 10.25 oz. to 13 oz. 

 Liebig's estimate makes the average quantity of carbon even 

 higher, namely 1 3 T 7 Q- oz., " which pass off through the skin and 

 lungs as carbonic acid gas."* His observations were made 

 on soldiers. He adds, on the authority of Boussingault, that 

 a horse consumes 79iV oz. of carbon in 24 hours ; a milch 

 cow, 70| oz. ; a pig fed with potatoes, 21^ oz. Were such a 

 quantity of carbon, to take the nearest round number at 

 80 oz., daily changed to carbonic acid in the horse, for the 

 purpose of animal temperature, it would suffice to raise 634 Ib. 

 of water a weight equal to that of a small horse from 100 

 Fahrenheit to the boiling-point. 



With regard to the second point above referred to namely, 

 the amount of heat yielded during the combustion of given 

 quantities of carbon and oxygen there appears to be at pre- 

 sent little difference of opinion among chemists. The state- 

 ment cited before, and used in the calculations made namely, 

 that the combustion of one oz. of pure carbon evolves heat 

 enough to raise the temperature of 14,200 times its weight of 

 water through one degree of Fahrenheit's thermometer accords 

 very well with the researches of Andrews, which Liebig adopts, 



* ' Familiar Letters on Chemistry,' p. 313, third edition. 



