THE BODY'S UTILIZATION OF FAT 429 



deposited in the degenerating cells. 3 The fat of different animals con- 

 sists of different proportions of the three common fats, olein, palmitin 

 and stearin. But for each animal the proportion in which the three 

 fats enter into its fatty mixture is fairly constant. Eecall the differ- 

 ence between beef and mutton tallow and lard. This proportion of fats 

 being fairly constant for an animal species, it does not change with 

 every change of diet. But if an animal be starved for a time and then 

 fed exclusively on a particular fat, such as some vegetable fat never 

 normally found in the animal, the fat used can be demonstrated as 

 present unaltered in the tissues. The question then of the origin of 

 tissue fat is st'ill somewhat uncertain. It seems safe to say that the 

 fat of the food can be deposited unaltered in the tissues, but that all the 

 fat found in the tissues has had its origin in fatty food is certainly 

 not the case ; much of it is made from carbohydrate and some of it may 

 be made from proteid. 



Turning to the question of the disposal of fat in the body, we may 

 say that it is completely burned in the tissues and has as its end 

 products carbonic acid and water. 



A moderate amount of fat in many tissues, especially the sub- 

 cutaneous connective tissues, the omentum and tissue about the kidney, 

 is normal, and serves as a store of energy, as a protective covering to 

 the body and to retain the body's heat. But there are many persons in 

 whom this amount is excessive, that is, in no way proportioned to their 

 needs. In seeking an explanation of these cases we are at once struck 

 with individual differences. For instance, one sees persons over whose 

 bodies there is a uniform thick layer of fat; they are of florid com- 

 plexion and many of them active persons. The term corpulent applies 

 to them better than obese, since their bodies exhibit both an increase 

 of fat and of protoplasm and their blood is of normal specific gravity. 

 In the presence of a good digestion and abnormal appetite, they daily 

 consume more food energy than the daily expense of energy requires. 

 The excess is laid away as tissue proteid and fat. A moderate diminu- 

 tion in food taken with some increase in exercise would rectify the con- 

 dition. But it is almost a waste of words to tell a man to eat less in 

 the presence of an excellent appetite and digestion. 



There are other persons in whom the picture is quite different. The 

 fat is not uniformly distributed, but is largely abdominal, the arms and 

 legs being little enlarged ; they are pale, and blood examination reveals 

 anemia and diminished specific gravity of blood. Herter calls atten- 

 tion to the rather striking parallel between this condition and diabetes. 

 In diabetes there is an excess of sugar in the body tissues. This has 

 been shown not to be due to any increase in sugar manufacture, but to 



" The question of the origin of fat from proteids is ably discussed by Henry 

 A. Christian, M.D., ' Some Newer Aspects of the Pathology of Fat and Fatty 

 Degeneration,' Bull, of Johns Hopkins Hosp., January, 1905. 



