THE ANIMAL AS A PRIME MOVER. 303 



the breakdown of tissue, to be produced. Beclard found the quantity 

 of heat developed by voluntary muscular contraction greater when 

 simply an effort is produced, as when grasping an object firmly, than 

 when doing work, as by lifting the object. Matteucci found that 

 muscles absorb oxygen and throw off carbon-dioxide when doing work, 

 and in larger amount as more work is performed. 



Dr. Flint, after a very beautiful investigation of the conditions of the 

 muscular system and the changes of tissue in the case of the pedes- 

 trian Weston after a five-days' walk, as well as throughout equal 

 periods during and before the tremendous effort which carried him over 

 117.5 miles at the mean rate of over 4 miles per hour of actual travel, 

 concluded that "work is always attended with destruction of muscular 

 substance,-" "the direct source of muscular power is to be looked for 

 in the muscle itself." He thinks that the muscular tissue "can not be 

 absolutely stationary, and disassimilation must go on to a certain 

 extent even if no work is done. This loss must be repaired by food to 

 maintain life." That this is ordinarily, or at least may be, a very small 

 proportion of the energy effect is evident from the well-known condi- 

 tions of hibernation and by the fact that Dr. Tanner and others have 

 fasted for 40 days and more with no great apparent loss of vital and 

 essential strength, and seemingly at only the cost of accumulated fat 

 disposed of as a superfluity, previously, in the spaces between the 

 muscles. In the case of severe labor, as where a pedestrian continually 

 exerted all his powers for days together, Flint has proven clearly that 

 large quantities of muscular tissue are broken down. 1 



The proportion of nitrogenized or muscle-making food to nonnitro 

 genized, in the walk here referred to, was, as measured in units of 

 energy, about as 5,700,000 foot-pounds to 39,000,000, or about 15 per 

 cent; which figure will be recognized later as corroborated by other 

 and independent methods of examination of this subject. The total 

 absorbed energy would thus be about 11,000,000 foot-pounds per day, 

 plus that derived by the breaking down of tissue to the extent of the 

 total value of about 3,500,000 foot-pounds, 700,000 per day; that is to 

 say, 11,700,000 foot-pounds of energy were supplied the system per day, 

 when doing au extraordinarily large amount of work, both externally 

 and internally. 2 But Weston is a small man, and probably 10 per cent 

 should be added to make these figures comparable with those elsewhere 

 given as the average for a workingman, 10,000,000 foot-pounds. This 

 gives a total of over 12,000,000 foot-pounds, or 20 per cent above the esti- 

 mated figure to be later computed for the average regular day's work. 

 The food taken averaged about 20 ounces, a pound and a quarter, but 

 was somewhat concentrated, and stimulating in more than ordinary 

 degree. 



1 The source of muscular power. New York: D. Appleton &■ Co. 1878. 



-The vital machine consists of about 40 per cent muscle, of which a half is water, 

 12.5 per cent blood, 2 per cent brain, and the remainder is skeleton and iuternal 

 organs. 



