242 THE ADRENAL SYSTEM AND VASOMOTOR FUNCTIONS. 



kind, and are perhaps specific to muscle. Especially must this 

 be the case since it possesses, we have seen, a special physical 

 attribute: i.e., the direct conversion of chemical energy into 

 mechanical work, without involving the corresponding evolution 

 of heat which oxidation elsewhere in the organism engenders. 

 The word "corresponding" is used because we must not lose 

 sight of the fact that considerable heat is produced during 

 muscular contraction, and, indeed, that it is subject to marked 

 variations under the influence of fatigue, tension, the state of 

 the blood, the work done, etc. Yet the heat evolved is not 

 commensurate with the muscular work done, and if we deduct 

 from the heat potential actually produced that which intra- 

 muscular combustion of waste-products incident upon increased 

 exertion entails an unproductive factor as regards work the 

 need of the direct conversion of chemical energy into mechan- 

 ical work i.e., contraction of the muscle will appear. 



One of the constituents of myosinogen upon which its 

 physical function depends must be glycogen, since it is the 

 constituent of muscle which diminishes during activity, while 

 it accumulates during rest. This body was shown by Claude 

 Bernard in 1848 to be formed in the liver-cells from food, 

 especially from sugars and starches, derived in turn from 

 glucose: one of the products of digestion. Herbivorous ani- 

 mals, such as oxen, horses, etc., i.e., those that only feed 

 upon substances that contain these hydrocarbons, are ob- 

 viously endowed with great muscular power. It is evident, 

 therefore, that the source of the energy to be ultimately trans- 

 formed into mechanical work must be stored in these vegetable 

 substances to a very great extent. Glycogen may not, how- 

 ever, migrate as such toward the muscular elements since it 

 would undergo oxidation in the blood; it is thought to be 

 retransformed into glucose by a ferment and distributed as 

 such to the muscular tissue, where it is again dehydrated 

 (C 6 H 12 6 H 2 = C 6 H 10 5 ) into glycogen, ready for func- 

 tional use. This question will be studied later on. 



Outside the organism lactic acid is known to be a product 

 of fermentation of glucose, dextrin, and glycogen; hence the 

 conclusion that sarcolactic acid is formed during muscular con- 

 traction. According to prevailing views, however, the evidence 



