440 LECTURE XIX. 



food, because the organism has lost the power of being able to utilize the 

 energy stored up in it. If, on the other hand, the grape-sugar is slightly 

 changed before its introduction into the organism of the diabetic, then the 

 tissues are capable of completely oxidizing it. 



If the animal oxidation took place merely as a result of the coming 

 together of oxygen and nutriment, it would be expected that when an 

 increased amount of the reacting substances was present, a more vigorous 

 oxidation would ensue. This is, however, not the case. Under normal 

 conditions, it is not possible to increase the amount of oxidation taking 

 place in the tissues by increasing the supply of oxygen and the amount 

 taken up by the blood. 1 Similarly, we are not able to increase the total 

 consumption of material very much by increasing the supply of carbo- 

 hydrate or fat. Only of albumin do we know that the amount present 

 governs somewhat the extent of the transformation. 



We know, to be sure, of compounds which are not attacked by oxygen 

 in neutral solutions, but are attacked in the presence of alkali. Pyrogallol 

 absorbs oxygen in alkaline solutions so vigorously that it is used for the 

 detection of small quantities of this gas. To be sure, we do not have free 

 alkali present in our tissues, but merely alkali carbonates. These also favor 

 such oxidations. Thus it is known that a solution of glucose and soda 

 absorbs oxygen from the air, 2 although the amount taken up is but slight. 

 Schmiedeberg 3 has shown, moreover, that benzyl alcohol in the presence 

 of water is not attacked by atmospheric oxygen, but is transformed to 

 benzoic acid when it is in a sodium carbonate solution exposed to the oxy- 

 gen of the air. This compound is also oxidized by the oxygen in the blood. 

 If benzyl alcohol is conducted, with blood containing oxygen, through the 

 kidneys or lungs of dogs or pigs, benzoic acid is formed; while if salicylic 

 aldehyde is employed in the above experiment, salicylic acid is formed to 

 some extent. The amount of acid obtained in each case is very small. It 

 is necessary to state in this connection that these experiments are by no 

 means sufficient to account for the combustion of the nutriment. They 

 merely show us that easily oxidizable substances are more readily acted 

 upon by oxygen, when contained in alkaline solutions, than in neutral or 

 even acid ones. They in no way refer to the oxidation of the more diffi- 

 cultly oxidizable foodstuffs. 



We are compelled to assume that either the oxygen is changed in the 

 tissues to a form in which it is more active than usual, or that the nutriment 

 is in some way changed by the activity of the cell, so that it is more readily 

 acted upon by oxygen. Or these two processes may take place side by 

 side in the cell. 



1 See Schaternikoff: Arch. Anat. Physiol. 1904, Suppl. 135. 



2 M. Nencki and N. Sieber: J. pr. Chem. 26, 1 (1882). 



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



