i GENEKAL PHYSIOLOGY OF MUSCLE 43 



introduced and that eliminated with the urine. They found that 

 this equilibrium was not much affected by days of rest, as com- 

 pared with working days, i.e. no perceptibly greater quantity of 

 nitrogenous substances was consumed during work. 



This result was confirmed by the later and more accurate 

 researches of Voit (1870-81). He found not only in dogs kept on 

 a constant diet, but in starving animals also, that the amount of 

 nitrogen excreted was not much increased by work, and that the 

 increment was in no case in ratio with the amount of work done. 



Experiments made on themselves by Fick and Wislicenus 

 (1685) supported this result. They climbed the Faulhorn, 1906 m., 

 in six hours, during which time they collected all the urine passed. 

 During the twelve hours preceding the climb and on the ascent 

 they took no nitrogenous foods, and lived solely on starch, fat, and 

 sugar. From the amount of nitrogen contained in the urine they 

 deduced the amount consumed during the climb. They further 

 calculated the amount of mechanical work accomplished by the 

 leg muscles of each, multiplying the body-weight by the height of 

 the mountain ; the work done by the other muscles was not calcu- 

 lated. From the combustion heat of the protein consumed during 

 the ascent they calculated the maximal yield that could be 

 obtained if the whole of the protein in the body were burned up. 

 The result showed that the work done on the climb far exceeded 

 that which could be performed by the decomposition and oxida- 

 tion of the protein consumed. From this they concluded that the 

 non-nitrogenous substances introduced with the food or stored in 

 the body as reserve materials supply energy which can be utilised 

 during work. 



The direct proof that it is principally the non-nitrogenous 

 substances (carbohydrates and fats) that are consumed during 

 work is derived from experiments on the respiratory gas-exchanges, 

 which show that while the elimination of nitrogen does not 

 increase perceptibly the excretion of carbonic acid and absorption 

 of oxygen do increase considerably during work (Pettenkofer and 

 Voit, 1866, and others). This agrees perfectly with what was 

 stated above in regard to the consumption of glycogen and fat in 

 muscular activity. 



What part, then, does the protein of muscle play in the per- 

 formance of its functions ? Since muscle consists principally of 

 proteins, which are the fundamental substrate of all living tissues, 

 it must be recognised that these substances play an active part in 

 all the internal processes that go on in muscle. 



Traube suggested that the proteins of living matter have the 

 task of carrying oxygen to the non- nitrogenous combustible 

 materials, but are not themselves decomposed. This agrees with 

 Pfliiger's general theory of the oxidation processes of the animal 

 body, according to which the intra-molecular oxygen, chemically 



