74 LECTURE IV. 



of the carbohydrate did not stop with the formation of the products 

 named, but acetic and formic acids were formed with consumption of 

 oxygen. It is at present hard to tell what part the alcoholic fermentation 

 plays in the living organism, or whether, in fact, it has any significance. 

 At all events, Stoklasa's observations include the possibility of energy 

 being produced without oxygen being supplied. The fact that the animal 

 organism evidently makes use of such simple decompositions as a source of 

 energy is shown by the interesting experiments of Hermann, Pfliiger, and 

 Bunge. Hermann 1 proved that a piece of extirpated muscle, from which 

 no more oxygen could be pumped out, could work in an atmosphere free 

 from oxygen and produce carbonic acid. Hermann at the same time 

 detected the formation of an acid (lactic acid). Pfliiger 2 succeeded in 

 keeping a frog alive for twenty-five hours at a temperature a few degrees 

 above the freezing-point of water in an atmosphere free from oxygen, 

 during which time the animal evolved a considerable amount of carbonic 

 acid gas. Finally G. V. Bunge 3 showed that a parasitic-worm of the cat, 

 Ascaris mystax, could survive for four or five days in a medium absolutely 

 devoid of oxygen, and move around in a very lively manner during that 

 time. It should by no means be concluded from these very interesting 

 experiments, that the animal organism performs its muscular work solely 

 at the expense of the energy set free by hydrolytic decompositions. 

 The amount of living force produced in this way would be altogether too 

 small. On the other hand, it is conceivable that the cell, by means of a 

 partial breaking down, that is to say, by a hydrolysis and subsequent 

 oxidation of the decomposition products, can increase when necessary the 

 amount of energy available. Thus 100 grams of glucose when completely 

 oxidized to carbon dioxide and water yield 3939 calories (= 1,674,000 

 kilogram-meters of work). By alcoholic fermentation, i.e., the hydrolysis 

 of 100 grams glucose into carbon dioxide and ethyl alcohol, only 372 

 calories (= 158,100 kilogram-meters of work) are liberated. 



As a result of work the muscular tissue, which is amphoteric, becomes 

 of acid reaction. This change is, at least to some extent, due to the 

 formation of lactic acid. Formerly it was believed that there was a direct 

 connection between the formation of the latter and the decomposition 

 of carbohydrates. More recently, however, this view has been strongly 

 combated. At present it has not been definitely decided as to what 

 relation the lactic acid bears to the performance of work by the muscles. 

 It is possible that its presence is due to a hydrolysis caused by the 

 absence of a sufficient amount of oxygen. On the other hand, it is also 

 conceivable that the formation of lactic acid has nothing whatever to do 



1 Untersuchungen iiber den Stoffwechsel der Muskeln, Berlin, 1867. 



2 Pfliiger's Arch. 10, 251 (1875). 



3 Z. physiol. Chem. 8, 48 (1883-84); 12, 565 (1888); 14, 318 (1889). 



