Current Comment

ORIGIN OF FECAL FAT  The products of digestion in the gastro-intestinal tract are not in the body until they have passed through the wall of the intestine. Two circumstances have combined to render difficult the precise determination of the so-called utilization of the major food materials and the evaluation of the factors influencing it; namely, the great difficulty in securing samples of blood and lymph at the immediate site of absorption from the intestine and the now well known fact that materials are excreted into the enteric canal as well as absorbed from it. Thus the fecal lipid may represent either unabsorbed fat, fat that has been excreted, or both. The presence of bile is an important factor in the digestion and absorption of fat ; in its absence there is a definite increase in fecal fat. In order to determine the origin of the lipid in the feces of subjects with bile fistulas, Shapiro and his co-workers ¹ have fed, together with the diet, fat containing a known proportion of deuterium. This isotope² of hydrogen apparently behaves as ordinary hydrogen in metabolism and yet can be quantitatively determined in compounds containing it ; it serves as an identifying "mark" for substances of which it is a part. The proportion of deuterium in the fecal fat equated