776 THE FORMATION OF FAT. [BOOK n. 



appropriate proportion, though their proportion in the food may 

 largely vary, and though some of them may be wholly absent. 

 Thus in one experiment the fat of the body contained considerable 

 quantities of stearin after a diet free from stearin, and in another 

 preserved the normal amount of olein after a diet free from olein. 



Of course it is quite possible that in such cases as these, though 

 the stearin, or the olein, when absent from the food, was in some 

 way or other constructed anew, yet at the same time those constitu- 

 ents which were present were simply stored up ; and the small 

 quantity of erucin present in the fat of the body after feeding 

 on erucin must have been directly stored up. So also, when an 

 animal is rapidly fattened on a diet consisting of a small quantity 

 of proteid and a large quantity of fat, the amount of fat stored up 

 may be too great to have come from the proteids of the diet, in 

 which case we may infer that it was the actual fat of the food 

 simply deposited in the fat-cells of the body. But even in this 

 case, as more distinctly in the others, it is also open for us to 

 suppose that all the fat taken as food was in some way or other 

 disposed of, and that all the new fat which made its appearance 

 was constructed anew. And the latter view is more perhaps in 

 harmony with the histological facts previously mentioned, as well 

 as supported by other considerations. 



At the present, however, we may be content with the following 

 conclusions. 1. < Fat is actually formed in the animal body, and 

 the fat present at any moment in the body is not exclusively, if at 

 all, fat merely stored up from the fat of the food.. 2. The carbon 

 elements of the newly-formed fat may be supplied ^either from 

 carbohydrate food, or from the carbon surplus of proteid food, or 

 from fats taken as food which are not the natural constituents of 

 the body-fat.^ 3. ( The fat stored up appears as fat granules or 

 drops deposited in the cell-substance of certain cells, and the 

 increase of the fat in the cells is accompanied first by a growth, 

 and subsequently by a consumption of the cell-substance ; but, as 

 in the analogous, case of glycogen, there is no complete evidence to 

 shew whether the fat granules which appear are simply deposited 

 by the cell-substance in a more or less mechanical manner, without 

 their forming an integral portion of that cell-substance, the chief 

 stages of the manufacture of the fat having been gone through 

 elsewhere, or whether they arise from a breaking up, a functional 

 metabolism of the cell-substance of the fat-cell itself; the latter 

 view is on the whole however the more probable. 



