444 LECTURE XIX. 



duced by means of partial decompositions. We should expect, therefore, 

 that hydrogen and other easily oxidizable substances would be formed. 



This was, however, not the case. The presence of hydrogen could not be 

 detected, nor did oxygen disappear, if oxygen was supplied after the worms 

 had existed for a day without it. Now we have no right to apply the 

 results of such experiments to human beings, or to other animal organ- 

 isms. The parasites of the intestine are accustomed to get along with a 

 very limited supply of oxygen. It is perfectly possible that their metabo- 

 lism takes place entirely differently than is the case with the remaining 

 animal organisms. Perhaps hydrolytic decompositions take place in 

 them without forming any easily oxidizable substances. Furthermore, 

 it is conceivable that these little worms normally have active oxygen at 

 their disposal, formed, at least to some extent, by the energetic reduction 

 processes which take place in the alimentary canal. On the other hand, 

 we must remember that the assumption of an activation of oxygen, by 

 means of the formation of reducing substances in the tissues, has never 

 gotten beyond the hypothetical stage. It is remarkable too that the 

 animal organism itself is able to keep easily oxidizable substances in its 

 tissues, such as phosphorus, for example, in an unchanged condition for 

 a considerable length of time. It is not easy to understand how such a 

 substance as this escapes the active oxygen unless it be assumed that 

 during its transport through the animal tissues, it never actually 

 comes in contact with nascent oxygen. Such an assumption seems 

 strained, for we know of countless examples in which the animal organism 

 is protected from poisons by their being oxidized. The oxidation does not 

 always take place to such an extent, but frequently it serves to prepare a 

 new substance which can become harmless by conjugation with something 

 else, whether it be glycocoll, sulphuric acid, glucuronic acid, or urea. On 

 the other hand, it is a fact that a reduction process may facilitate the 

 combination of the poison with one of the above compounds. At all 

 events, it is extremely interesting to find that these oxidations are quite 

 different in various cases. At one time the compound may be completely 

 oxidized, whereas, in another case, merely an atom of oxygen may be 

 added to its composition. We can, indeed, believe that the cells, as 

 already mentioned, may regulate their decompositions by means of their 

 ferments; but it remains an enigma, according to the assumption of the 

 presence of active oxygen, why the oxidation should stop at a certain 

 stage in the case of readily oxidizable substances, whereas in other cases 

 a total oxidation takes place. 



Unquestionably, we would prefer an hypothesis which in itself includes 

 this regulation of the extent of oxidation. The first suggestion of such an 

 hypothesis was made by Moritz Traube. 1 He pointed out the important 



1 Theorie der Fermentwirkungen. Berlin, 1858. 



