FATTY ELEMENTS OF FOOD, AND ON FATTENING. 419 



is consumed by a true process of combustion, which converts its 

 carbon into carbonic acid, and its hydrog^en into water ; or otherwise, 

 it is simply eliminated without change in the urine. 



Fatty matters may, indeed, disappear under the first form ; but 

 so long as they escape remarkable modification, it is certain that 

 they do not pass off by the urine, and that the quantity eliminated 

 by the perspiration is insignificant. Their insolubility, therefore, 

 retains tbem in the economy once they have entered the blood or 

 the tissues ; and it is in virtue of this quality that they constitute a 

 kind of magazine of combustible matter in the animal body. This 

 is the principal reason wherefore individuals supplied with food in 

 excess get fat, and that those insufficiently fed fall lean ; the fatty 

 matter being deposited in the interstices of the tissues in the former 

 case, being taken up from them and burned in the second. 



This explanation is attractively simple ; but in our attachment to 

 it we must not forget that other explanations have also been given ; 

 and in particular it must be contrasted with a view which has been 

 formed upon certain inquiries undertaken by M. Dumas. It is 

 known, for instance, that sugar may be regarded as a compound of 

 carbonic acid, water, and defiant gas. Now there is nothing to pre- 

 vent olefiant gas becoming detached and taking different states of 

 condensation, to give rise to bodies which by undergoing oxidation 

 would produce fat acids and consequently fats. Since it has been 

 known that the oil of potato spirit is also met with in the spirit obtain- 

 ed from the refuse of the grape, and in the spirit procured from 

 malt, and from the molasses of beet-root sugar, the assurance that 

 the oil is a product of the fermentation of sugar appears to be com- 

 plete. 



We ought even to be prepared to admit a phenomenon of the same 

 kind as taking place in plants, when we see the sugar of their stems 

 disappearing in the same ratio as their seeds or fruits become charg- 

 ed with oleaginous njatter : all the palms elaborate sugar before 

 producing oil. 



It is upon chemical views of this kind that the second opinion as 

 to the source of fat in animals has been formed, and which may be 

 said to stand in direct contrast with that which assumes this sub- 

 stance as pre-existing in the food, which regards it as produced in 

 the blood itself, under the influences of the most intimate forces of 

 animal life. For my own part, I adopt the view which supposes dn 

 animal to be supplied with fat already formed, mainly because it 

 presents itself to me as more in harmony with the facts which T 

 observe in our stables. Still I do not deny that it may be possible 

 for a certain quantity of fat to be elaborated in the bodies of herbi- 

 vorous animals, under the influence of a special fermentation of the 

 sugar which forms an element in their food ; although I feel satisfied, 

 from practical facts, that sugar plays no essential part in the fatten- 

 ing of cattle. 



The formation theory, nevertheless, is not without data of a very 

 curious and important kind, which require notice. Huber had found 

 that bees fed upon honey, and even upon sugar, did not lose the 



