102 
MUSCULAR WORK 
calories. Assuming a respiratory quotient of 0.90, the calorific equivalent 
of 91.2 liters of oxygen would be 449.1 calories and of 53.6 liters, 263.9 calories, 
so that it can be seen that of the excess of oxygen consumed, approximately 
5.5 per cent was used for mechanical work, and of the total consumption of 
oxygen less than 3.3 per cent. 
Following the experiments of Lavoisier and Seguin, no data from which 
the efficiency of the body can be computed were obtained until the experiments 
of Edward Smith. From the results obtained by Smith and by Despretz 
and Dulong, 6 Helmholtz c computed that of the total heat incidental to the 
performance of muscular work, one-fifth is used for mechanical work and 
four-fifths are given off in the form of heat, thus showing a gross efficiency of 
the body of 20 per cent. 
Haughton, in an address before the British Medical Association at 
Oxford, d calculated the average daily labor of a man to be 109,549 kilogram- 
meters, or the work necessary to raise a man of 150 pounds of weight to the 
height of 1 mile, and that the heat produced in 24 hours would be the equiva- 
lent of six times the average mechanical work performed by a laboring man. 
Thus he considers that the gross mechanical efficiency would be equal to 
17 per cent. 
Basing their computations upon the utilization by the body of 300 grams 
of carbon in the ascent of Mont Blanc, Dumas and Boussingault computed 
the efficiency of the body as 33 per cent. 6 
Table 101. — Mechanical efficiency of the human body as computed by Him. 
Subject. 
Work in 
1 hour.* 
Oxygen 
consumed. 
Carbon 
dioxide 
excreted. 
Q 
r2 
kgm. 
gms. 
gms. 
cals. 
42 years 
+27,581 
126.80 
174.35 
233.10 
0.217 
+27,448 
130.95 
180.06 
251.60 
0.204 
+23,257 
115.72 
159.12 
203.50 
0.212 
-26,972 
63.71 
87.60 
351.50 
0.220 
47 years, laborer 
+32,550 
123.68 
170.06 
229.40 
0.250 
-30,275 
59.86 
81.90 
251.60 
0.394 
+25,912 
99.12 
136.29 
192.30 
0.172 
+22,987 
88.63 
121.87 
268.30 
0.167 
+19,586 
85.55 
117.63 
214.60 
0.176 
-24,175 
49.57 
68.16 
251.60 
0.292 
i + = positive work; — = negative work. 
. „. . . , ,, _ . Kgm. work . / _ , Kgm. work\ 
2 Him designates by r the gross efficiency, i. e., j^z -5- I Q H j^= I . 
In 1857 a French physician in Colmar, Hirn/ attacked the problem of 
the mechanical efficiency of the body from the experimental standpoint. 
Considering Q as all the heat losses of the body, such as radiation, the warm- 
ing of the expired gases, perspiration evaporated, etc., and T the work, he 
calculated that the total heat production of the body would be equal to 
Q-\-(Ts- 425). Hirn's results are given in abstract in table 101. There is 
obviously a great discrepancy between the calorific values of the oxygen 
a Smith, Edward, Philosophical Transactions, 1859, 149, p. 681. 
6 Despretz, Ann. de Chim. et de Phys., ser. 2, 1824, 26, p. 337 ^Dulong, Ann. de Chim. et de Phys., ser. 3, 1841, 
1, p. 440. 
c Helmholtz, Proc. Royal Institution, 1861, 3, p. 347. 
d Haughton, Relation of food to work, Dublin, 1868. 
< Dumas and Boussingault, Essai de statique chimique des fitres organises, 1844. Cited by Amar, Le rende- 
ment de la machine humaine, Paris, 1910, p. 21. 
/ The first work of Hirn on the human motor was published in the Comptes rendus de la Soc. de physique de 
Colmar, 1857. See, also, Hirn, Theorie m6canique de la chaleur, Paris, 1857, 1. 
