456 LECTURE XIX. 



from isobutylacetic acid. There seems to be an intimate relation to the 

 urea formation. The NH 2 and CO groups leave the molecule of the amino 

 acid at one time. With the proof of the acetone formation from products 

 obtained from albumin, we obtain for the first time a clear idea concerning 

 the utilization of the carbon chains free from nitrogen from certain amino 

 acids. We learn in this way to consider the formation of acetone as a 

 normal process, it being an intermediate product in the decomposition of 

 leucine. One source of acetone is thus established. Perhaps from this 

 stage in the breaking down of the amino acids we can trace their relation 

 to the carbohydrates and fats. 



We do not yet know how the preliminary preparation of the glucose 

 molecule for oxidation is effected. In the case of the fatty acids, however, 

 we are justified in assuming that oxidation is preceded as above described 

 by a cleavage between the a and ft carbon atoms. It seems probable that 

 the eventual oxidation always takes place with products having but few 

 carbon atoms in the chain. With these presumptions, we can at least 

 draw a picture of the oxidation processes in the animal organism, which 

 will at least not contradict any known facts. The cells prepare substances 

 for oxidation as they require energy. They cannot effect the oxidation of 

 d-leucine, for example, because no ferment is present which is capable 

 of breaking the molecule down sufficiently to make the oxygen accessible 

 to it. The cells do their work in stages. At any moment the decom- 

 position may be stopped, and the products already formed, used for new 

 syntheses. They do not decompose suddenly. We cannot by any means 

 compare the oxidation in the animal organism with a conflagration. 

 Everything is regulated to the most minute detail. Cleavage and oxida- 

 tion take place alternately, so that the cell can utilize the energy it obtains 

 from step to step, and only in this way is it possible to regulate so care- 

 fully the heat supply. 



The difficulties which are met with in attempting to explain animal, 

 as well as vegetable, oxidations, have led to various hypotheses which depend 

 upon the fact that the difficultly oxidizable substances are made capable 

 of taking up oxygen directly only by means of some function exerted by 

 the protoplasm. These attempts at explanation, however, do not rest 

 upon any experimental basis. They are far in advance of our knowledge 

 concerning the nature of the cell-protoplasm. It is for this reason that it- 

 is so difficult to submit them to experimental proof. O. Loew l traces 

 the oxidation to the unstable condition of the albuminoid in protoplasm. 

 It transfers the lively movement of the atoms in the active albumin mole- 

 cule to the oxygen and the oxidizable substance. In this way there is a 

 loosening up of the molecule, so that the atom of oxygen is offered a point 



1 Ber., 35, 2487 (1902). cf. E. Wolff: Die chemische Energie der lebenden Zellen. 

 Munich, 1899. 



