248 



SCIENCE. 



[X. S. Vol. XXI. No. 529. 



as seems warranted by the studies of com- 

 bustion. It is worthy of note also that the 

 late steps in the process, the hydrolysis of 

 g:lucose by zymase, have been designated by 

 the term fermentation. The combustion of 

 starch has likewise not been examined, but 

 as the end products are identical with those 

 of digestion, it is not at all improbable that 

 the intermediate steps are the same, though 

 they succeed one another too fast to be fol- 

 lowed by means at present available. 



I need hardly remind you that our pres- 

 ent ideas of the dynamics of chemical reac- 

 tions forbid us to believe that such dissocia- 

 tion does not go on slightly at lo^v tempera- 

 tures, even when unaided. But it is so 

 slow^ as to be ordinarily beyond our meas- 

 urement. The enzymes seem to be mere 

 accelerators of the several processes, per- 

 haps preparing 'compatible systems,' as 

 high temperature may do in combustion ; 

 perhaps entering into union with the sub- 

 stance they act on and forming compounds 

 which are dissociable at ordinary tempera- 

 tures in appreciable amounts. 



The clue to an understanding of respira- 

 tion has been found, therefore, not by com- 

 paring it to combustion, which was so long 

 misleading, but by assimilating combustion 

 to respiration. We may hope that eliemists 

 will restrict the term combustion or intro- 

 duce a new one that will make more obvious 

 the mode of action. Physiologists at least 

 will do well to drop 'combustion' altogether 

 from their vocabulary, as neither the past 

 conception of it nor its probable use in the 

 future conduces to clearness of thought. 



NATURE OF ANAEROBIC RESPIRATION. 



The third line of advance has been in a 

 study of the relations of fermentation and 

 anaerobic respiration. The first step was 

 that long-sought discovery by Buchner, 

 that the process of fermentation by yeast 

 is brought about by the action of an enzyme 

 which breaks up certain hexose sugars into 



carbon dioxid and alcohol. But a fur- 

 ther step in advance has lately been taken. 

 It appears from the work of Buchner and 

 Meisenheimer* that the alcoholic fermenta- 

 tion is not direct, but that it occurs always 

 in indirect fashion, as shown below. 



cHo OH coon 



I OH I 



CHOH CHOH 



CHOH H CHj 



I H I 



CHOH OH CO 



I OH I 



CHOH CHOH 



1 I 



CHjOH H CH, 

 H 



glucose water hypo- 

 thetical 

 substance 



COOH 

 CHOH 

 (■H3 



OH CO J 

 H 



CHjOH 



H CH3 CH, 



OH COOH OH CO, 



I 



H 



CHOH 

 I. 



CH, 



(•H„OH 



I 



CH, 



2 mols. carbo i 



lactic acid dioxid 

 and ethyl 

 alcoliol 



Stepanek has reached the same con- 

 clusion,! and Maze J has found acetic acid 

 as an intermediate product in alcoholic fer- 

 mentation by a different yeast. The in- 

 terest of the discovery that inactive ethyl- 

 idene lactic acid is the intermediate sub- 

 stance in this process of fermentation lies 

 in the fact that one of the two acids of 

 which that is composed, namely, d-ethyl- 

 icleue lactic acid or sarcolactic acid, is 

 formed as a product of respiration when 

 proteids break down in the working, fa- 

 tigued, or dying muscle. Fletcher ob- 

 served this as a more prominent product 

 of contracting muscles than carbon dioxid 

 itself. Thus a regular product of fermen- 

 tation is also formed in the ordinary course 

 of respiration. 



The analogy between anaerobic respira- 

 tion and fermentation had been suggested 

 early —even by Pasteur— and has thus been 

 growing closer with each added bit of 

 Icnowledge. But the precise way in which 

 the destruction of the living substance went 

 on in anaerobic respiration was still un- 



* ' Dip cheinisclien Vovgiinge bei alcoholischen 

 Giiruno;.' Jici: Dculsch. Chcin. GescUs. 37: 419- 

 428. 1904. 



t ' Ueber die aerobe imd anaerobe Atmiing der 

 Eier.' Centralbl. Physiol. 18: 188-205. 1904. 



t ' Utilization dii carbone ternaire.' Atm. Inst. 

 J'astcin: 18: 277-30.3. 1904. 



