4 INTRODUCTION 



to be easily oxidized or autooxidized, and the process is considered as a 

 direct oxidation or autooxidation. As the oxygen of the inspired air ; 

 and that of the blood, is neutral molecular oxygen, the old assumption 

 that ozone occurs in the organism has now been discarded for several 

 reasons. On the other hand, the chief groups of organic nutritives, 

 carbohydrates, fats, and proteins, the last two forming the chief mass 

 of the animal body, are not autooxidizable substances. They are on 

 the contrary bradoxidizable (TRAUBE) or dysoxidizable bodies. They 

 are nearly indifferent to neutral oxygen, and it is therefore a question 

 how an oxidation of these and other dysoxidizable bodies is possible 

 in the animal body. 



In explanation it is very generally admitted that the oxygen is made 

 active and this causes a secondary oxidation. It is generally con- 

 ceded that in autooxidation a cleavage of neutral oxygen takes place. 

 The autooxidizable substance splits the oxygen molecule and combines 

 with one of the oxygen atoms, while the other free atom as active oxygen 

 may oxidize the dysoxidizable substances simultaneously present. Such 

 a subordinate oxidation is called an indirect or secondary oxidation. 

 The explanation of animal oxidations has been attempted in different 

 ways by the supposition that the oxygen is made active and thus pro- 

 duces secondary oxidation. 



The cause of the animal oxidation is considered, by PFLUGER and 

 several other investigators, to be dependent upon the special constitu- 

 tion of the protoplasmic proteins or the living protoplasmic substance. 

 This investigator calls the proteins outside of the organism, or those 

 which occur in the animal fluids, " non-living proteins," and considers 

 them to be somewhat different from those occurring in living protoplasm. 

 The latter are called " living proteins " (PFLUGER), " active proteins " 

 (LoEw), or " biogens " (VERWORN). The living protoplasmic molecule 

 differs from the ordinary non-living protein by being more unstable and 

 therefore having a greater inclination toward intramolecular changes 

 of the atoms. 



The reason for these greater intramolecular movements PFLUGER ascribes to 

 the presence of cyanogen, and LATHAM attributes it to the presence of a chain 

 of cyanalcohols in the protein molecule. VERWORN, 1 on the contrary, claims 

 an intramolecular introduction of oxygen into a large hypothetical protoplasmic 

 molecule, the " biogen molecule," which is supposed to contain a nitrogen or an 

 iron complex as an oxygen receptor or carrier, and a side-chain of aldehydic 

 character like that of the carbohydrates, as an oxidizable group. 



According to LoEW, 2 who bases his claim upon special investigations and 



1 Pfliiger, Pfliiger's Archiv, 10; Latham, Brit. Med. Journal, 1886; Verworn, 

 Die Biogenhypothese, Jena, 1903. 



2 Loew and Bokorny, Pfliiger's Archiv, 25; O. Loew, ibid., 30; and specially O. 

 Loew, Die chemische Energie der lebenden Zellen. 2. Aufl. Stuttgart, 1906. 



