896 PHYSIOLOGY 



acidosis is more easily brought about by ingestion of butyric 

 acid than of the higher acids, such as palmitic or stearic, suggest- 

 ing that whatever fatty acid is given it is finally reduced to 

 butyric acid before its oxidation, and that in the condition of acidosis 

 it is merely the last stages of this oxidation which are at fault. We 

 are thus justified in concluding that the oxidative breakdown of 

 fats occurs always by an oxidation in the ft position. 

 We take, for instance, the 6-carbon stage : 



CH 3 . CH 2 . CH 2 . CH 2 . CH 2 . COOH 



the first change which probably occurs is the oxidation : 

 CH 3 . CH 2 . CH 2 . CH 2 OH . CH 2 . COOH 



A further change is the complete oxidation of the last two groups 

 and the production of butyric acid : 



CH 3 .CH 2 .CH 2 .COOH 



This then undergoes again oxidation in the /3 position, with the 

 production of /3-oxybutyric acid : 



CH 3 .CHOH.CH 2 .COOH 



and then again is converted to diacetic acid, 



CH 3 .CO.CH 2 .COOH 



In the normal individual this last stage undergoes complete 

 oxidation, both oxybutyric acid and diacetic acid given to a healthy 

 person being completely destroyed in the body. It is only under 

 the abnormal conditions which we have mentioned above that these 

 last stages fail of complete oxidation, and are excreted unchanged in 

 the urine. 



THE QUESTION OF THE FORMATION OF SUGAR FROM FAT 



The ease with which the animal body performs the difficult chemical 

 operation of transforming carbohydrate into fat suggests that under 

 appropriate conditions it might effect the reverse change. Is there 

 any evidence that in the animal body sugar may be derived from 

 fat ? Such a conversion is of normal occurrence during the ger- 

 mination of fatty seeds, starch sugar and cellulose being formed at 

 the expense of the stored-up fats of the seeds. If such seeds be allowed 

 to germinate over mercury in a confined volume of xygen, they 

 are found like seeds containing chiefly carbohydrate reserves, to 

 absorb oxygen and to give off carbon dioxide. Whereas, however, in 

 the latter case the amount of carbon dioxide evolved is almost equal 

 to the oxygen absorbed, in the case of the fatty seeds much less 



