MUSCLE. 269 



was not by any means compensated by the consumption of proteid. 

 It was therefore proved by this that albumin alone cannot be the 

 source of muscular activity, and that this depends in great measure 

 on the metabolism of non-nitrogenized substances. Many other ob- 

 servations have led to the same result, especially the experiments of 

 VOIT, of PETTENKOFER and VOIT, and of other investigators, whose 

 experiments show that while the elimination of nitrogen remains un- 

 changed, the elimination of carbon dioxide during work is very con- 

 siderably increased. It is also generally considered as positively 

 proved, that muscular work is produced, at least the greatest part, 

 by the metabolism of non-nitrogenized substances. Nevertheless 

 we are not warranted in the statement that muscular activity is 

 produced entirely at the cost of the non-uitrogenized substance, and 

 that the albuminous bodies are without importance as a source of 

 force. 



Among the non-nitrogenized bodies we must accord to carbo- 

 hydrates, glycogen, and sugar the first place as sources of force. 

 The fact that the carbohydrates are consumed during exertion has 

 been previously discussed, and their great importance as a source 

 of activity is generally admitted. The most important is glycogen, 

 not only that which pre-exists in the muscles, but also that which 

 is contained by the liver and conveyed by the blood to the muscles 

 as sugar to be used in muscular work. If the consumption of 

 carbohydrates in activity is positively proved, then the question 

 arises whether the quantity of glycogen or carbohydrates which is 

 at the disposition of the muscles is sufficient for the development 

 of the living force produced within them. Though it is difficult to 

 give a positive answer to this question, it still seems certain that, 

 at least in some particular cases, the carbohydrates are not sufficient 

 for the development of this force. According to statements whose 

 correctness cannot be doubted, muscles free from glycogen can per- 

 form work (BERNARD, LUCHSINGER). 



Even though no direct investigations on removed muscles have 

 shown any increase in the consumption of fat during activity, still, 

 from the above-mentioned experiments on the exchange of material, 

 we conclude that the fats are also undoubtedly sources of muscu- 

 lar force. In regard to the albuminous bodies we have no positive 

 direct observations which tend to establish the importance attrib- 



