i GENEKAL PHYSIOLOGY OF MUSCLE 39 



utilised by the muscle during work. Nasse (1869) first pointed 

 this out, as he found that the glycogen content of muscle is in 

 inverse ratio with the work performed. The best evidence for it 

 lies in the fact that all muscles prevented from working by section 

 of their nerves or tendinous attachments contain an excess of 

 glycogen, as compared with the symmetrical muscles that have 

 remained intact (MacDonnel, Chandelon, Manche, Weiss, E. 

 Krauss). At the same time it is a striking fact that muscular 

 glycogen diminishes far more slowly than hepatic glycogen in 

 fasting (Weiss, Aldehoff, Luchsinger) ; this is not due to the fact 

 that the liver normally supplies the muscles with glycogen, since 

 even when the liver has been excised the glycogen-content of the 

 muscles can be increased by feeding with cane-sugar/ Muscles 

 have therefore an amylogenic and glycogenic function which is 

 perfectly independent of that of the liver (Prausnitz). 



Helmholtz (1845) observed that during tetanus the extractives 

 of muscle which are soluble in water diminish, while those soluble in 

 alcohol increase, which depends at least in part on the reduction of 

 glycogen and increase of glucose coincident with muscular activity. 



Lactic (or sarcolactic) acid is an important constituent of 

 muscle ; during rigor mortis it may amount to O'l-l'O per cent 

 (Bohm, Demant). Living, resting muscle has a neutral or feebly 

 alkaline reaction, while rigid muscle has a distinctly acid reaction. 

 Muscle plasma, too, is first neutral or feebly alkaline, and becomes 

 acid after coagulation. The cause of this reaction has been the 

 subject of much controversy. Some authors have tried to replace 

 Liebig's early theory (1847) that it is due to a development of 

 lactic acid, by the hypothesis that the acidity of muscle is caused 

 exclusively by mono-phosphate of potassium. This can only be 

 proved by excluding the formation of lactic acid during the life of 

 the muscle. It may, however, be assumed that the free lactic 

 acid, acting on the potassium bi-phosphate of normal living 

 muscles, is converted into potassium lactate, by reduction of the 

 neutral into acid phosphate, which may partly account for the 

 acidity of dead muscle. 



It was formerly, and is still sometimes held (Araki), that 

 lactic acid arises from disintegration of the glycogen. But this 

 is obviously controverted by the work of Bohm and of Demant. 

 Bohm (1880) showed that the amount of lactic acid formed during 

 the death of the cat's muscle is in no relation with the glycogen 

 content, since the latter gradually disappears during starvation, 

 while the proportion of lactic acid is not less than normal. Demant 

 (1879) showed that glycogen entirely disappears in the pectoral 

 muscle of pigeon after eight days of fasting, while there is a free 

 formation of lactic acid. From these results they concluded that 

 the mother-substances of the lactic acid formed by muscle must 

 be sought in its proteins. 



