ANIMAL OXIDATIONS. 451 



substance. Again, the manganese dioxide decomposes with loss of oxygen, 

 and in this way the splitting off of oxygen by the ferment containing the 

 manganese is effected. Such views are, however, very improbable, because, 

 according to the researches of Chodat and Bach, the oxidases containing 

 manganese obtained from plants are inactive in the absence of peroxidases. 

 The peroxidases themselves have the function of activating the oxidases, 

 for in the great dilution in which they are present in the juices and cells, 

 the latter do not readily give up their oxygen from the peroxide formation. 

 The action of the peroxidases may be compared with the decomposition 

 of peroxides by means of ferrous salts. 



With the help of these hypothetical representations we are able to see 

 how the cells are not only able to regulate carefully the hydrolytic decom- 

 positions caused by ferments, but also the oxidations as well. The latter 

 are directly dependent upon the formation of the peroxidases. Now the 

 observations upon which this line of reasoning is advanced have been 

 made upon plants, but there is little doubt that the animal cells conduct 

 their oxidations in much the same way. All this, however, is purely 

 hypothetical. It should always be taken into consideration that all 

 experiments conducted in the study of the action of oxidases have been 

 with substances which are oxidized without much difficulty. The com- 

 bustion of such important foodstuffs as albumin, fat, and carbohydrate 

 is still an obscure process. We do not know definitely in what manner the 

 oxidizing destruction takes place. It is clear to us, from this discussion, 

 that the metabolism which takes place within the cells is infinitely com- 

 plicated, and that in the establishment of the fact that oxygen is taken 

 up and carbon dioxide eliminated, nothing whatever was determined as to 

 the real root of the matter. We are now beginning to understand at how 

 many places the mechanism concerned in the cell-decompositions may be 

 disturbed and how diverse these disturbances may be. 



In the light of our present information concerning the breaking down 

 and combustion of the separate foodstuffs in the animal organism, we 

 may safely assume that the preliminary stage of practically all decompo- 

 sitions is a hydrolysis. First of all the foodstuffs are subjected to hydro- 

 lytic cleavage. According to all our present knowledge, amino acids are 

 formed from albumin, glucose from glycogen, and glycerol and fatty acids 

 from the fats. We must assume that the other substances which play a 

 part in the metabolism of the organism are prepared for combustion in an 

 entirely analogous manner. We know that the nucleins are decomposed 

 into albumin and nucleic acid, and that these are again broken down into 

 their simpler components. Purine bodies are thus formed, 1 which we 

 believe first lose their nitrogen group and are then prepared for oxidation. 

 In this case we can establish very accurately the moment at which oxygen 



1 See Lecture XIII, p. 292. 



