464 MUSCLE-NERVE PHYSIOLOGY 



There is then a greater proportion of carbon dioxide produced in muscle 

 during activity than during rest. 



During rigor mortis there is also an increased production of carbon dioxide. 



Second, muscle during rest produces nitrogenous crystallizable substances, 

 such as creatin, from the metabolism which is constantly going on in it during 

 life; in addition there are formed, in all probability, sarcolactic acid and 

 other non-nitrogenous matters. 



During activity the nitrogenous substances, such as creatin, undergo 

 very slight, if any, increase about the amount produced during rest but 

 the sarcolactic acid is distinctly increased; sugar (glucose) is also increased, 

 whereas the glycogen is diminished. 



During rigor mortis the sarcolactic acid is increased, and in addition 

 myosin is formed. 



From these data it is assumed that the processes which take place in 

 resting and active muscles are somewhat different, at any rate in degree. 

 From actively contracting muscle, also, there are obtained an increased 

 amount of heat and mechanical work; potential energy is converted into 

 kinetic energy. 



Many theories have been proposed to explain the facts of muscular energy. 

 It has been suggested by Herman that muscular activity depends upon the 

 splitting up and subsequent re-formation of a complex nitrogenous body, 

 called by him Inogen. When this body so splits up there result from its 

 decomposition carbon dioxide, sarcolactic acid, and a gelatino-albuminous 

 body. Of these the carbon dioxide is carried away by the blood stream; the 

 albuminous substance and possibly the acid, at any rate in part, go to re- 

 form the inogen. The other materials of which the inogen is formed are 

 supplied by the blood; of these* materials we know that some carbohydrate 

 substance and oxygen form a part. The decomposition, although taking 

 place in resting muscle, reaches a climax in active muscle, but in that con- 

 dition the destruction of inogen largely exceeds restoration, and so there must 

 be a limit to muscular activity. But this is not the only change going on in 

 muscle, there are others which affect the nitrogenous elements of the tissue, 

 and from them result the nitrogenous bodies of which creatin is the chief; 

 these changes may be unusually large during severe exercise. 



It has been further suggested as myosin is undoubtedly formed in rigor 

 mortis when the muscle becomes acid and gives off carbon dioxide, and since 

 myosin is formed also when muscle contracts, that the phenomenon of 

 contraction is a condition akin to partial death. The electrical reactions 

 appear to justify this; both contracted and dead muscle are negative to 

 living muscle when at rest. What happens to the myosin which is formed 

 when muscle contracts, if this view be the correct one, is unknown. Halli- 

 burton suggests that the myosin, which can be made to clot and unclot easily 

 enough outside the body, is able to do the same thing in the body. It is pos- 



