SUPPLEMENT 61 



this results in the formation, on the one hand, of carbon-dioxide and on the 

 other of an oxidizable body which, in presence of oxygen, is oxidized. We must 

 not assume that this body is always the alcohol which appears in intra-mole- 

 cular respiration that, in other words, alcohol is always the intermediate 

 respiratory product. There are many facts which contradict such a view, but 

 the alcohol may indeed owe its existence to a subsequent alteration of the 

 hypothetical primary oxidizable body. The essential point in this idea lies 

 in the assumption that respiration consists of two processes, which are not 

 necessarily inseparable splitting and oxidation. What facts, then, can be 

 advanced in support of there being two such processes concerned ? In the first 

 place, we must recall the results arrived at by PURIEWITSCH, which went to 

 show that the formation of CO 2 and the absorption of O are in ordinary respira- 

 tion much more independent of each other than we have hitherto been 

 led to suppose ; and in the second place, we would draw attention to 

 the fact established by PALLADIN and PETRACHEWSKY that Chlorothecium , 

 when kept for a long time in an atmosphere of hydrogen, gives off very 

 much more CO 2 than usual when again placed in oxygen. That may be 

 explained by assuming that a certain amount of readily oxidizable substance 

 is produced, whose further decomposition is rendered possible on the addition 

 of oxygen . 



If respiration really consists in two processes, then the problem as to its 

 cause would appear to be not simplified but rendered more difficult. This is 

 not the case, however. Many more recent researches, which certainly have 

 often the character of ' preliminary notes ', and which are often contradictory, 

 render it more and more probable that, as in the metabolic processes previously 

 studied, enzymes play a chief part in this one also, and that these, independently 

 of the living protoplasm, effect the formation of CO 2 from organic substances. 

 These enzymes are, perhaps, not so readily extracted from the cell as so many 

 other hydrolytic enzymes, for they are often unable to pass through the cell- 

 wall (comp. however, RACIBORSKI, 1905), and perhaps, generally speaking, are 

 not so soluble in water as they are. Hence we are even less able, in this case, 

 than in that of the hydrolytic enzymes, to isolate them in the pure condition. 

 The existence of a respiratory enzyme may be, indeed, clearly demonstrated 

 in the following ways : (i) by vigorously grinding the cells, so that as many as 

 possible are broken open, and subjecting them to great pressure (BUCHNER, 

 1903) ; (2) by rapidly killing the cells either by chemicals, such as ether and 

 acetone (ALBERT, 1901), or by cold (PALLADIN, 1905). By the first method one 

 obtains an expressed sap, by the second closed but dead cells. In both cases 

 it can be shown that oxidation goes on though micro-organisms be carefully 

 excluded. We may select from the abundant literature the experiments of 

 MAXIMOW (1904) with the expressed sap of Aspergillus niger. This sap exhibits 

 a gaseous exchange, after the addition of sugar, which entirely corresponds to 

 that of respiration, oxygen being taken in and carbon-dioxide being given off. 

 That this respiratory process is due to the action of two enzymes, however, one 

 of which induces splitting and the other oxidation of the products of splitting, 

 is proved by the fact that the evolution of CO 2 continues when oxygen is re- 



CO 



moved by a stream of hydrogen, and that the value of the fraction -^ rapidly 



2 



falls. The latter fact is explained by the more rapid inhibition of the splitting 

 enzyme than of the oxidizing one. There is nothing extraordinary in this 

 destruction of the enzyme, since the sap contains a mixture of many bodies, 

 from which digestive enzymes are never absent, and enzymes are in all proba- 

 bility digestible proteids. 



One of these splitting enzymes inducing the formation of CO 2 (carbonases : 

 PALLADIN, 1905) is exactly known, viz. the so-called zymase of BUCHNER, 



