218 ANNUAL OF SCIENTIFIC DISCOVERY. 



MENTAL LABOR MORE EXHAUSTING THAN PHYSICAL LABOR. 



Prof. Haughton, the well-known scientist, of Trinity College, Dub- 

 lin, in a recent paper, asserts that a man who labors neither bodily 

 nor mentally, but who merely lives, will excrete, for every pound of 

 his weight, two grains of urea per diem. Thus, a man weighing 150 

 pounds, and engaged in no physical or mental employment, will ex- 

 crete 300 grains of urea. The urea being the products of the com- 

 plete decomposition of one of the nitrogenous animal tissues, it is 

 necessary that the man should consume a quantity of food capable 

 of yielding an amount of nitrogen equivalent to that contained in 300 

 grains of urea. This quantity of food suffices, according to the pro- 

 fessor, to keep alive 150 pounds' weight of man, and the work done 

 by the food is termed by the professor opus vitale. In the case of a 

 working man of standard (150 pounds) weight, the amount of motive 

 power developed by him is indicated by the quantity of urea elimi- 

 nated from his body, which, in the case of hard-working laborers, is 

 about 400 grains. We find, then, that a man employed in manual 

 labor, of an uniutellectual character, must employ a quantity of food 

 sufficient, by its decomposition, to yield 400 grains of urea, and of 

 this quantity of aliment three-fourths are expended in keeping the 

 body alive, and the remaining fourth in mechanical work opus me- 

 clianicum. A man engaged in mental labor eliminates a quantity of 

 urea varying, according to Prof. Haughton's experiments, from 486 

 grains to 510 grains ; clearly proving that mental work causes a much 

 greater waste of tissue than manual labor. 



Professor Haughton states that men employed in mere manual 

 routine labor require only a vegetable diet, whilst those who are en- 

 gaged in pursuits requiring the constant exercise of the intellectual 

 faculties must be supplied with food of a better kind. 



INFLUENCE OF THE LABOR OF THE TREADWHEEL OVER RES- 

 PIRATION AND PULSATION, AND ITS RELATION TO THE 

 WASTE OF THE SYSTEM AND THE DIETARY OF THE 

 PRISONERS. 



The following inquiries in reference to the above subject were 

 made by Dr. Edward Smith, of England, on his own person, in Oc- 

 tober, 1856, at the Coldbath-fields prison. He worked the wheel 

 during periods of a quarter of an hour each, with intervening periods 

 of rest of a quarter of an hour, in the manner prescribed for the 

 prisoners, and made seven series of observations. The average 

 quantity of air breathed during the labor was 2,500 cubic inches per 

 minute, at a rate of respiration of twenty-five and a half per min- 

 ute, and a depth of respiration varying from 91^ cubic inches to 107|- 

 cubic inches. The rate of pulsation varied from 150 to 172 per min- 

 ute. During the intervals of rest he sat quietly, and after thirteen 

 minutes' rest the rate of restoration varied from fifteen to eighteen 

 and a half per minute ; the quantity of air respired from 725 cubic 

 inches to 980 cubic inches ; the depth from 48 cubic inches to 53 

 cubic inches; and the rate of pulsation from 97 to 120 per minute. 

 Before he entered upon the inquiry, he breathed, in the standing 



