THE FOOD REQUIREMENT OF THE SICK 45 



of intestinal secretions, and do not contain remnants of food. These condi- 

 tions are realized only when absorption is normal and the food is suitable. 



This assumption, however, is not true in health if the diet contains sub- 

 stances in a form difficult of absorption. In the sick, in whom the mechan- 

 ism of digestion as well as the mechanism of absorption is disturbed, the 

 estimation of the food lost in the feces is absolutely necessary, for we cannot 

 estimate it by simple subtraction. 



The analysis of feces is therefore very important in all quantitative clin- 

 ical investigations of metabolism. The results, compared with an exact esti- 

 mation of the food ingested, give a clear idea of the amount of food assim- 

 ilated in the intestinal canal. 



Voit demonstrated in his laboratory the energy-value of the food of healthy 

 persons by thus estimating the part which remained undigested in the intes- 

 tine and in the feces when the subject was given various diets, simple -or mixed. 

 This forced us to investigate the manifold pathologic conditions which com- 

 plicate the mechanism of digestion and the processes of absorption and to 

 study the absorption of and utilization of food in these conditions. 



The researches undertaken in this direction are extremely numerous, and 

 only their most important results can be summarized here.' 



In by far the majority of these studies we have limited ourselves to esti- 

 mating accurately the nitrogen and the fat during the period of investigation. 

 In view of the fact that the disappearance of carbohydrates during their pas- 

 sage through the intestinal canal is accomplished not only by absorption 

 through the intestinal mucous membrane, but also by decomposition (fer- 

 mentation), and hence that the residue of carbohydrates found in the feces 

 does not give a reliable measure of the actual amount used, carbohydrate esti- 

 mation in feces has been quite commonly neglected in these investigations. 

 Only lately A. Schmidt ^ has minutely investigated this question, and in his 

 " fermentation test " has given a method for determining accurately those 

 portions of the undissolved carbohydrates which are susceptible to the fluids 

 of digestion, yet have escaped absorption. His proposition to utilize always 

 the same trial meal (qualitative and quantitative) for the quantitative estima- 

 tion of the absorption of albumin and fat in disease deserves the fullest 

 consideration. 



The investigation of the absorption of food in pathologic conditions, in so 

 far as technic and quantitative estimation are concerned, has now reached a 

 high degree of perfection. 



Comparatively few of the numerous researches in metabolism have given 

 noteworthy and positive results concerning the assimilation of food. 



The researches of Fr. Miiller ^ in the metabolism in jaundice, which are 

 the earlier quantitative investigations at the bedside, should be mentioned 

 first, since they determine a very important decrease in fat absorption in 

 eases of occlusion of bile from the intestine. 



14. Schmidt, Deutsches Arch. f. klin. Med., Bd. Ixi, pp. 280 und 545; Verh. gr. f. 

 inrikre Med., 1898 und 1899. 



2 Fr. Miiller, " Untersuchungen uber Ikterus." Zeitschr. f. klin. Med., Bd. xii, p. 45. 



