PARENTERAL FAT ABSORPTION 379 



not otherwise make much change in the relative transforma- 

 tion processes. Above all, however, the wear on the cor- 

 poreal mechanism will be manifest in a nearly constant 

 nitrogenous output. 1 



Importance of Lipoids in Nutrition. Is fat a vitally nec- 

 essary food? We formerly were disposed to deny this ques- 

 tion without hesitation, because it was well known that dogs 

 can be readily kept alive and strong for a long time on meat 

 diet alone. However, recently W. Stepp, in investigations, 

 undertaken under direction of Franz Hofmeister, has 

 brought out the remarkable fact that mice invariably die if 

 their appropriate food be freed of all fatty substances by 

 thorough alcohol-ether extraction. If pure neutral fat (tri- 

 palmitin, tristearin or triolein), or lecithin or cholesterol or 

 even butter, be added to the degreased food, the animals con- 

 tinue to die; apparently it is not the well-defined fats but 

 certain "lipoids" which are essential for maintenance of 

 life. This is only another example of the peculiar things 

 which one is sure to encounter in the course of metabolism 

 studies. 2 



Parenteral Fat Absorption. If it is desired to introduce 

 large amounts of fat into the body apparently the only way 

 is by the bowel, and, perhaps, too, by intraperitoneal intro- 

 duction. Experimental subcutaneous injection of olive oil, 

 and, similarly, stained and iodized fat, has invariably shown 

 that only very small amounts of such substances (at best no 

 more than a few grams per diem) can be absorbed from the 

 subcutaneous tissue, the bulk otherwise remaining unchanged 

 in situ. On reflection it may be readily appreciated that the 

 injected fat in all likelihood (just as the fat of the organized 

 depots) can be absorbed only after it has been changed to a 

 soluble form by some lipolytic ferment. However, a large 



1 Literature: Graham Lusk, Ernahrung and Stoffwechsel, 2d ed. (German 

 Translation by L. Hess), pp. 149-154, 1910. 



a W. Stepp (Hofmeister's Lab., Strassburg), Biochem. Zeitschr., 22, 452, 

 1909; Zeitschr. f. Biol., 57, 135, 1911. Cf. also W. Stepp (Med. Clinic, Giessen, 

 Voit), XXIX Kongr. f. innere Med., Wiesbaden, 1912, p. 610. 



