35G THE MUSCLE-TISSUE. 



described, while a second portion is allowed to remain exposed to 

 the air for a few hours. Both portions are then examined for 

 glycogen, when it will be seen that only the first gives a positive 

 reaction. (As regards the details of the method, see page 403.) 



GLUCOSE. 



That traces of glucose and maltose may be found in fresh muscle- 

 tissue is, of course, not surprising in view of the above considerations. 

 To demonstrate their presence, the fresh material is finely hashed, 

 placed in boiling water, and boiled for a few minutes. On cooling, 

 the mixture is filtered, the filtrate concentrated to a small volume 

 and examined in the usual manner. Larger quantities may be 

 obtained if the finely minced tissue is placed in chloroform- water 

 and autodigestion is allowed to proceed for several weeks. 



LACTIC ACID. 



The reaction of living muscle-tissue while at rest is neutral or 

 slightly alkaline. After death, however, it becomes acid, and it 

 can then be demonstrated that the acidity is in part, at least, refer- 

 able to paralactic acid. Through the action of the latter upon 

 dipotassium phosphate monopotassium phosphate then results, and 

 a second factor thus appears, to which the acid reaction is due. 



Formerly it was supposed that rigor mortis was the result of the 

 formation of lactic acid, but we now know that this is not the case, 

 and that the coagulation of the muscle-tissue precedes the appearance 

 of the acid reaction. To use the words of Salkowski, the muscle does 

 not form lactic acid because it dies, but because it lives, and only as 

 long as it lives. With the occurrence of its death the formation ceases. 

 This is, therefore, a vital or ultravital process, and there is abundant 

 evidence to show that this view, which is now quite generally accepted, 

 is correct. Under ordinary conditions it is difficult to show that 

 acid material is produced while the muscle is at work, as it is then 

 removed by the circulation as rapidly as formed; but if this is 

 prevented, the fact can readily be demonstrated. To this end, one 

 sciatic nerve of a rabbit is divided and the animal poisoned with 

 strychnin. If then the muscles of both legs are removed during the 

 final convulsions of the animal, it will be noted that the reaction of 

 those groups which had remained in connection with their nerve- 

 supply is distinctly acid, while the others, the nerve of which was 

 severed, show a neutral reaction. That the acid reaction in such 

 cases is, in part at least, actually due to lactic acid, can be shown by 

 extracting the rested and the tetanized groups with water and then 

 with alcohol. On evaporating the resulting extracts and weighing 

 the corresponding residue it will be noted that the weight of the 

 alcoholic fraction is greater in the case of the worked muscle than 



