THE PROCESS OF OXIDATION. 231 



the latter disappears from the circulation, if we remember that this 

 sugar, when associated with an alkali, is capable of taking up 

 combined oxygen, and of withdrawing it from oxide of copper and 

 many other oxides. 



Our experiments show that a less striking influence is ex- 

 erted by the alkalies on the oxidation of the fats and fatty acids ; 

 indeed, direct observations appear to show that the fats in the blood 

 are oxidized much less rapidly than the carbo-hydrates, or even 

 than the albuminous substances. Urea may be detected in urine 

 as a product of the oxidation of the nitrogenous matters of the 

 food, long before the combustion of the fats can be recognised in 

 the augmentation of the expired carbonic acid (see Nutrition) ; 

 whilst facts may be advanced in proof of the gradual oxidation 

 experienced by the fats under the action of an alkali and oxygen. 

 We need only refer to the occurrence in the blood of acids homo- 

 logous to the solid fatty acids, as for instance, in certain secretions, 

 and more especially in the sweat, where the whole series of acids, 

 from formic to caproic acid, has been exhibited with tolerable cer- 

 tainty. Thus, too, butyric fermentation, like lactic fermentation, 

 requires the addition of equivalent quantities of the alkalies for its 

 perfect accomplishment. Although we may deny the appellation 

 of fats to those lipo'ids, such as cholesterin and serolin, which most 

 probably are formed only in the blood, they betray in many of 

 their properties so near an affinity with these bodies, that in our 

 ignorance of their origin, it would scarcely seem at variance with 

 the truth, were we to refer them to the oxidation of the fats as 

 residua poor in oxygen, in the same manner as we refer humus to 

 the decomposition of wood. 



Chevreul and Scherer have recently shown that hcematin (the 

 colouring matter of the blood) when dissolved in alkalies is able to 

 continue unchanged for a prolonged period, and that on the access 

 of atmospheric air it instantly attracts oxygen, and becomes con- 

 verted into a colourless body. The want of a more careful exami- 

 nation of these facts has hitherto prevented the exact comparison of 

 this form of metamorphosis with that which occurs in the 

 blood. 



No one can doubt that the albuminous substances of the blood 

 undergo a gradual oxidation before they can be employed in the 

 formation or renovation of the tissues, although we certainly are 

 still unable to determine the extent to which the alkalies influence 

 their oxidation and further metamorphosis. We know only this 

 much, that the alkali of the blood must aid in abstracting and 



