51 
page 49, of his “Theorie,” it will be seen, however, that lie employs 
the term “ Sauer stojf ubertragenden Fermente ” (oxygen-carrying fer- 
ments) for the vegetable oxygen carriers described by Planche and 
Schoenbein, and later, in 1874, in an article on the conduct of yeast 
in oxygen-free media ( 429 ), referring to his earlier work, he says: 
I have given several examples to show that there are substances (in animal and 
vegetable tissues) which, like platinum, nitric oxide, and indigo-sulphuric acid, carry 
free oxygen to other substances and thereby accomplish their oxidation. ( Sauer - 
stoffiibertrager, oxydations fermente.) 
It was in his later writings ( 43 °) , however, especially in his contro- 
versy with Hoppe-Seyler that he insists upon the use of the term 
Oxydationsfer merit e (oxidizing ferments) as preferable to the term 
V erw esun gsfer merit e, which latter term he had previously employed 
as signifying those ferments which possess the power of taking up 
free oxygen and carrying it to other passive substances, thereby 
accomplishing the oxidation of the latter. 
As the result of their action, the oxidizing ferments suffer no chem- 
ical alteration, playing merely the part of go-betweens in oxidation, 
in that they alternatel} 7 combine with oxygen and give it up to other 
substances. Obviously, according to Traube, free oxygen is essential 
to their action. In this connection his earlier observations on the 
oxidizing ferments of the potato are of interest. He showed that if 
thinly cut potato peel is rubbed up in a mortar with a small amount 
of distilled water, a solution is obtained which blues guaiacum in- 
tensely. If the blue solution thus obtained be allowed to stand in a 
reagent glass it bleaches, except on the upper surface vdiere it is in 
contact with the air. On shaking with air, however, the vdiole solu- 
tion again acquires a deep blue color, which on standing again 
bleaches. This alternate bluing of the solution by shaking with air 
and subsequent decolorization of the lower layer of the solution upon 
standing was observed upon one and the same solution for a period 
of fourteen days, indicating that the potato peel contained a true 
oxygen carrier through the instrumentality of which the oxygen of 
the air was transferred first to the guaiacum and subsequently to 
other substances. He also showed that the potato loses its power 
to blue guaiacum at 80° C., and that the unstable oxygen carrier 
which it contains is soluble in dilute alcohol. He points out that a 
body of such remarkable chemical conduct and of such wide distribu- 
tion in the plant kingdom must play a significant role in the growth 
of vegetation. Similarly, he also recognized the red coloring matter 
of the blood as a powerful oxygen carrier, and w^as led to regard mus- 
cular activity as a respiratory act in which the muscle fiber functions 
as an oxidizing ferment in that it unites with the oxygen supplied by 
the blood to form an unstable compound, which in turn gives up its 
oxygen to other less readily oxidizable compounds contained in the 
L _ 
