ANIMAL OXIDATIONS. 445 



of oxygen carriers. In the study of inorganic chemistry, we know of 

 various processes which take place in the presence of a carrier of oxygen, 

 but will not take place from direct contact with oxygen. An example of 

 such a process is in the oxidation of glucose by potassium indigo sul- 

 phonate, or by copper oxide. If a solution of glucose is warmed with 

 alkali carbonate in the air for some time, practically no oxygen is taken 

 up. As far as we can see, the glucose remains unaffected. Now if we add 

 a little potassium indigo sulphonate to the solution, in the course of a 

 short time the blue solution becomes decolorized, and the amount of 

 unchanged glucose remaining in the solution gradually becomes smaller 

 and smaller. The glucose has become oxidized. If now we shake the 

 solution, it soon turns blue again, but again on standing it becomes color- 

 less. At the same time, more of the glucose becomes oxidized. This 

 process may be repeated again and again, until finally no more glucose 

 remains. A very small amount of potassium indigo sulphonate suffices 

 to cause the oxidation of a large amount of glucose. Copper oxide exerts 

 a perfectly similar effect. An ammoniacal solution of cupric oxide 

 becomes decolorized on warming it with glucose. The cupric oxide is 

 converted into cuprous oxide, or, in other words, the copper is reduced. 

 Oxygen has been furnished to the glucose molecule. If the decolorized 

 solution is exposed to the air for some time, gradually, and first at the 

 places where the solution is in direct contact with the air, it turns blue 

 again. Oxygen is thus being taken up by the cuprous oxide, which may- 

 be given up subsequently to more glucose. The whole process can be 

 accelerated considerably by shaking the liquid with air. 



It is not difficult to conceive that substances are present in the animal 

 tissues which act as carriers of oxygen for the more difficultly oxidizable 

 substances. As we have said, a very small amount of such substances 

 suffices to accomplish an indefinite amount of oxidation. The carrier 

 itself is in the same condition at the end of the process that it was at the 

 beginning. Now we know that ferments play an important part both in 

 the animal and vegetable kingdoms. The thought naturally arises that 

 perhaps certain of these ferments may act as carriers of oxygen. Traube 

 speaks of oxidizing ferments. Recently Schmiedeberg l has mentioned 

 the possibility of certain definite oxygen-carrying ferments; while Jaquet 2 

 has followed up this suggestion and succeeded in proving that extracts 

 of the organs serve as carriers of oxygen, and that in fact the principle 

 which causes this action may be precipitated by means of alcohol without 

 its losing any of its power of causing oxidation. Heating to 100 C., 

 however, destroys it. 



To-day, no one doubts that a great many such ferments are actually 



1 Arch, exper. Path. Pharm. 14, 288 (1881). 

 3 Ibid. 29, 386 (1892). 



