BIOLOGY. 



285 



But the actual working power of tlie human body does not ap- 

 proach this. In fact, altliough a man's daily hibor has a very 

 large range, as from 300,000 foot-pounds when lifting dung into a 

 cart to 1,500,000 foot-pounds when pushing or pulling horizontally, 

 yet the average is not above 1,000,000 foot-pounds, as will be seen 



from this diagram : — 



Kind of Labor. 



Bricklayer's laborer carrying bricks, . 



Coal whipping, ..... 



Ascending Faulhorn, .... 



. « « • 



Treadmill, ..... 



<< 



Turning a winch, .... 

 Pedestrians (20 miles a day), . 

 Paving and pile-driving, . . . 

 Porters carrying loads, . . . 

 Shot drill punishment, . . . 



Average, ..... 



Amount of Work 

 in foot-pounds. 



, 1,627,200 



, 1,293,600 



1,074,931 



933,746 



1,008,000 



861,156 



837,760 



792,000 



788,480 



732,480 



694,400 



Authority. 



Mayhew. 



Wislicenus. 



Fick. 



Mayhew. 



Ed. Smith. 



Coulomb. 



Haughton. 



Coulomb. 



Haughton. 



967,614 



And even when we add the calculated internal work of a man's 

 body, as the beating of the heart and the movements of respira- 

 tion, the total of it does not much exceed 1,500,000 foot-pounds a 

 day: — 



Foot-pounds. 



External work or actual labor, ...... 967,614 



Work of circulation (75 beats a minute), .... 497,880 



Work of respiration (15 a minute), ..... 98,064 



Total ascertainable work per day, 



1,563,558 



It is evident, therefore, that a large portion of our food must 

 escape digestion and absorption ; indeed, the thermotic power of 

 the food actually consumed daily, as estimated by the carbonic 

 acid exhaled, and the urea secreted, is not more than sufficient to 

 raise the temperature of 10,000 pounds of water 1° F. This is 

 equal to a force of 7,720,000 pounds lifted a foot high ; so that the 

 ascertainable work of the food is about one-fifth of its actual ener- 

 gy, the rest of the power being consumed in molecular move- 

 ments within the animal body. Helmholtz asserts that the exter- 

 nal work should be a fifth part of the mechanical force of the 

 digested food ; but labor must be well applied to develop this pro- 

 portion of its energy. — Scientific American. 



ON THE RELATION OF HEAT TO MENTAL WORK. BY J. S. LOM- 

 BARD, M.D. 



The influence of muscular contraction on animal temperature 

 has been very carefully investigated, especially within the past 

 few years ; and it has been conckisively proved that a contracting 

 muscle evolves heat. Furthermore, the relation between the heat 



