178 
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. (I) 2 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. Bokor?iy {2) 
and by W. Pfeffer . (3) 4 Neither could it be discovered in animal 
cells. Reinke's 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 (4) assumes the existence of oxidising 
enzymes, which would act as transporters of oxygen, somewhat 
like nitric oxide in the manufacture of sulphuric acid. (5) 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. 18S3. Nr. 5 and 6. 
(2) Ber. Deutsch. Chem. Ges. 21 , 1100 and 1848. Prhigsh. Jahrb. iy, 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. Clio , 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 [Vries), the oxidation of aniline by a slight trace of 
ammonium vanadate (Bull. soc. chim. 45,309) or the oxidation of nitrogenous com¬ 
pounds when added to a solution of oxide of copper in ammonia exposed to air (O. 
Lociv , 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. 
