224 PHYSIOLOGICAL CHEMISTRY 



of agar-agar 1 has been suggested. 2 This agar is relatively indigestible 

 and readily absorbs water (about 16 times its weight), thus forming a 

 bulky fecal mass which is sufficiently soft to permit of easy evacuation. 

 The function of agar is not limited to its use in connection with consti- 

 pation; it may serve in other capacities as an aid to intestinal therapeu- 

 tics by serving as a vehicle for certain drugs. 3 



It is frequently desirable for clinical or experimental purposes to 

 make an examination of the fecal output which constitutes the residual 

 mass from a certain definite diet. Under such conditions, it is custom- 

 ary to cause the person under observation to ingest some substance, at 

 the beginning and end of the period in question, which shall sufficiently 

 differ in color and consistency from the surrounding feces as to render 

 comparatively easy the differentiation of the feces of that period from 

 the feces of the immediately preceding and succeeding periods. One 

 of the most satisfactory methods of making this " separation" is by 

 means of the ingestion of a gelatin capsule containing about 0.2 gram of 

 powdered charcoal at the beginning and end of the period under observa- 

 tion. This procedure causes the appearance of two black zones of char- 

 coal in the fecal mass and thus renders comparatively simple the 

 differentiation of the feces of the intermediate period. Carmine (0.3 

 gram) may be used in a similar manner and forms two dark red zones. 

 Some similar method for the "separation of feces" is universally 

 practised in connection with the scientifically accurate type of nutrition 

 or metabolism experiment which embraces the collection of useful data 

 regarding the income and outgo of nitrogen and other elements. 



Among the macroscopical constituents of the feces may be men- 

 tioned the following: Intestinal parasites, undigested food particles, 

 gall stones, pathological products of the intestinal wall, enteroliths, 

 intestinal sand, and objects which have been accidentally swallowed. 



The fecal constituents which at various times and under different 

 conditions may be detected by the use of the microscope are as follows : 

 Constituents derived from the food, such as muscle fibers, connective- 

 tissue shreds, starch granules, and fat; form elements derived from 

 the intestinal tract, such as epithelium, erythrocytes, and leucocytes; 

 mucus; pus corpuscles; parasites and bacteria. In addition to the con- 

 stituents named the following crystalline deposits may be detected: 

 cholesterol, koprosterol, soaps, fatty acid, fat, hematoidin, l( triple phos- 



1 Agar-agar is a product prepared from certain types of Asiatic sea- weed. It is a carbo- 

 hydrate and is classified as a galactan in the polysaccharide group. 



2 Mendel: Zent.f. ges. Physiol. u. Path, des Stofw., No. 17, p. i, 1908; Schmidt: Munch, 

 med. Woch., 52, 1970, 1905. 



3 Einhorn: Berl. klin. Woch., 49, 113, 1912. 



