NON-NITROGENIZED CONSTITUENTS OF THE BODY. 441 



and analogous observations have been made upon birds and mammals, by 

 Boussingault. Under certain conditions more fat exists in the bodies of ani- 

 mals than can be accounted for by the total quantity of fat taken as food 

 added to the fat existing at birth. In experiments with reference to the in- 

 fluence of different kinds of food upon the development of fat, it has been 

 ascertained that fat can be produced in animals upon a regimen sufficiently 

 nitrogenized but deprived of fatty matters ; but the fact should be recognized 

 that " the nutriment which produces the most rapid and pronounced fatten- 

 ing is precisely that which joins to the proper proportion of albuminoid sub- 

 stances the greatest proportion of fatty matters " (Boussingault). 



There can be no doubt with regard to the formation of fat in the organ- 

 ism from albuminoid matters. Where an excess of such matters is taken as 

 food, it is probable that the albuminoid substance is decomposed, and that a 

 part of it is either deposited as fat or is oxidized into carbon dioxide and 

 water, and a part is discharged from the body in the form of urea. 



Theoretical considerations point to starch and sugar as the constituents 

 of food most easily convertible into fat, as they contain the same elements, 

 though in different proportions ; and it is more than probable that this view 

 is correct. It is said that in sugar-growing sections, during the time of 

 grinding the cane, the laborers become excessively fat, from eating large 

 quantities of saccharine matter ; and although there are no exact scientific 

 observations upon this point, the fact is generally admitted by physiologists. 

 Again, it has been frequently a matter of individual experience that sugar 

 and starch are favorable to the deposition of fat, especially when there is a 

 constitutional tendency to obesity. Carbohydrates added in quantity to a 

 nitrogenized diet favor the formation of fat. The fat may be formed from 

 the carbohydrates either directly (Lawes and Gilbert) or indirectly. If 

 formed indirectly, it is probable that the carbohydrates are oxidized into car- 

 bon dioxide and water, and that this saves, to a certain extent, destruction of 

 albuminoids. The. albuminoids are split up into fats, which are deposited 

 in the body, and into urea. 



Fatty degeneration occurs in tissues during certain retrograde processes. 

 The muscular fibres of the uterus, during the involution of this organ after 

 parturition, become filled with fatty granulations. Long disuse of any part 

 will produce such changes in its power of appropriating nitrogenized matter 

 for its regeneration, that it soon becomes atrophied and altered. A portion of 

 the nitrogenized constituents of the tissue, under these conditions, is changed 

 into fatty matter. The fat is here inert, and it takes the place of the sub- 

 stance that gives to the part its characteristic properties. These changes are 

 observed in muscles and nerves that have been long disused or paralyzed. 

 If the change be not too extensive, the fat may be made to disappear and 

 the part will return to its normal constitution, under appropriate exercise ; 

 but frequently the alteration has proceeded so far as to be irremediable and 

 permanent. 



It is difficult to explain the tendency to obesity observed in some indi- 

 viduals, which is very often hereditary. Such persons will become fat upon 



