THE ENERGY OF THE LIVING PROTOPLASM. 



oxidation in contact with molecular oxygen, so as to produce 

 peroxide of hydrogen, which under the influence of enzymes would 

 bring about powerful oxidations. 111 But Reinke omitted to prove 

 that the supposed " autoxidisers " would be really capable of 

 inducing oxidations of sugar or fat, while as regards that perox- 

 ide its absence in plant-cells has been proved by Th. Bokomy {Z) 

 and by W. Pfeffer. {:,) Neither could it be discovered in animal 

 cells. Rcinkcs view moreover could not explain how respiration, 

 throughout such a wide range, is independent of the amount of 

 oxygen present. But the belief that there exist in many plants 

 easily oxidisable compounds is no doubt true. Many plant juices 

 acquire soon a reddish or brown coloration, if exposed to air, a 

 phenomenon which illustrates how different a course is that 

 taken by respiration proper, since these same compounds were 

 no doubt formed in the protoplasm and afterwards gradually 

 secreted into the vacuole. Numerous plants, however, do not 

 yield a juice of like behaviour, nor has this been observed in 

 animal juices. Reinke's observations have therefore no connec- 

 tion with the respiration process. 



The theory of Traube {A) assumes the existence of oxidising 

 enzymes, which would act as transporters of oxygen, somewhat 

 like nitric oxide in the manufacture of sulphuric acid. (3) The 

 occurrence of such enzymes was not proved by Traube, but has 

 been demonstrated a year ago beyond any doubt by Toyonaga, who, 

 at my request, made a series of investigations. These enzymes 

 are the cause of the darkening of the juices of many plants when 

 easily oxidisable matters are present, as in potatoes, in the roots 



(1) Botan. Zeitg. 1SS3. Nr. 5 and 6. 



(2) Ber. Deutsch. Chem. Ges. 21, 1100 and 1848. Priugsh. Jahrb. 17, 347- 



(3) Ber. Sachs. Akad. d. Wiss, 1889. Recently the presence of H2 O2 in various 

 plants has again been asserted by Bach, but his reaction was unreliable (cf. Cho, this 

 bulletin, and his conclusion not justified). 



(4) Theorie der Fermentwirkungen, Berlin, 1858. Virch. Arch. 21, 386. Ber. 

 D. Chem. Ges. 10, 984. 



(5) Analogous processes are the action of ferrous salts in the oxidation of 

 tartaric acid in sunlight {Vrics), the oxidation of aniline by a slight trace of 

 ammonium vanadate (Bull. soc. chim. 4.5,309) or the oxidation of nitrogenous com- 

 pounds when added to a solution of oxide of copper in ammonia exposed to air (O. 

 Locw, Z. Biol. (1878) ; Journ. f. prakt. Chem. 1878). Another example, sometimes 

 cited, viz., the oxidation of indigo-white and its regeneration by alkaline glucose 

 solution is for obvious reasons not well suited for comparison in this connection. 



