l8o THE ENERGY OF THE LIVING PROTOPLASM. 



days standing, almost completely; dilute sulphuric acid and 

 caustic potassa acted in the same way, so that there can be 

 hardly any doubt that the active principle is an enzyme. 



Oxidising enzymes appear to be present also in the animal 

 body. Saliva produces a blue colour with Wurstcr's reagent 

 (tetramethylparaphenylene-diamine), a fact erroneously taken to 

 be a proof of the presence of hydrogen peroxide ; it produces 

 further a brown colouration with hydroquinone. E. Salkowski 

 found in the blood, Jaquet and also Yamagiwa in the lungs, 

 kidneys, and muscles, enzyme-like agencies, capable of producing 

 small quantities of benzoic acid from benzyl alcohol and of 

 salicylic acid from its aldehyde. (I) But such actions of enzymes 

 are always of a very narrow compass ; they belong to very weak 

 oxidations of certain benzene compounds, but never to an attack 

 upon, to say nothing of a complete combustion of, sugar or fat. 

 We must therefore reject also the theory of Traube as wholly 

 unsatisfactory. 



It appears singular that the authors mentioned all ignored 

 just the most important condition for respiration, i.e., the living 

 stale of the protoplasm. Taking a plain chemical start and leaving 

 physiology aside, they endeavored to reach a satisfactory expla- 

 nation, biased by the idea that the albuminous compounds the 

 chemist studies in his vials are the same as those composing 

 living matter. This erroneous conception still governs the 

 minds of many, and by them respiration will never be com- 

 prehended. 



It was Pfliiger who in the year 1876 drew the inference in 

 plain and forcible logic that the proteids of the living protoplasm 

 are different from those of the dead, and that their chemical 

 change into the indifferent common proteids signifies the death 

 of the cells. Only those chemical qualities exhibited by the 

 living cells can induce respiratory activity. " Oxygen is not 

 made active, but the proteids of the living cells have the 

 activity." Thus, a new foundation was gained, but few physio- 

 logists took notice of it ; above all, however, Ncncki assented. 

 Detmcr modified PJIiiger's view, assuming a continuous dissociation 



(1) Jahresb. f. Thierchem., 22, 387. Also Rdkmann and Spitzer: Ber. Chem. 

 Ges., as, 5 6 7- 



