124 PHYSIOLOGY AT THE FARM. 



blood thrown upon it at that moment. As the addition of the 

 oxygen afforded by oxide of copper in the destructive distilla- 

 tion of a piece of muscle diminishes the number of products, 

 so that nearly the whole of the carbon of the piece of muscle 

 is converted into carbonic acid, and nearly the whole of its 

 hydrogen into water, with the conversion of its nitrogen into 

 cyanate, or some other compound of ammonia, so in the dis- 

 integration of the living muscular fibre under its contraction 

 in the presence of the oxygen of the blood, there are few other 

 products than carbonic acid and water, while its nitrogen passes 

 into cyanate of ammonia or urea. 



Thus the arterial blood, in parting with its oxygen during 

 the contraction of a muscular fibril, acquires water and carbonic 

 acid, together with compounds of ammonia. The loss which 

 the blood itself sustains in parting with its oxygen has not yet 

 been fully ascertained. If, however, the general system is not 

 to suffer loss, that disintegration consequent on the contrac- 

 tion even of a single muscular fibril must be ere long compen- 

 sated for by a new deposition from the blood. Whence some 

 idea may be formed of the extensive disintegration necessarily 

 arising when, under violent muscular exertion, numerous mus- 

 cular fibrils are undergoing repeated contractions. 



It is to be remarked also that the disintegration here spoken 

 of is the' disintegration of the solid organism that which re- 

 quires for its repair not such proximate principles in organic 

 food as sugar, starch, oil, but such as albumen, fibrine. caseine. 

 It thus also appears why, if the bodily frame is to be main- 

 tained without loss of substance, the allowance of food must 

 be proportionate to the amount of muscular exertion which the 

 animal has put forth in a given time. At what a cost of food, 

 then, must long journeys on foot be maintained, if the oxen are 

 not to suffer a loss of weight ! 



Animal Temperature. It remains to be noticed how the 



