232 INTESTINAL DIGESTION 



The proportions of water and solid matter in the feces are variable. 

 Berzelius found in the healthy human feces, 73.3 parts of water and 

 26.7 parts of solid residue. The average of seventeen observations by 

 Wehsarg was the same. In the observations of Wehsarg, the mean 

 quantity of solid matter discharged in the feces in the twenty-four 

 hours was 463 grains (30 grams), the extremes being 882.8 grains (57.2 

 grams), and 251.6 grains (16.28 grams). The proportion of undigested 

 matters in the solid residue was very small, averaging but little more 

 than ten per cent, the mean quantity in the twenty-four hours in ten 

 observations being but 52.5 grains (3.4 grams). This was found, how- 

 ever, to be very variable; the largest quantity being 126.5 grains (8.2 

 grams), and the smallest, 12.5 grains (0.8 1 gram). 



Microscopical examination of the feces reveals various vegetable and 

 animal structures that have escaped the action of the digestive fluids. 

 Wehsarg also found a " finely divided fecal matter " of indefinite struc- 

 ture, but containing partly disintegrated intestinal epithelium. Crystals 

 of cholesterin were never observed. Whenever the matter is neutral or 

 alkaline, crystals of ammonio-magnesian phosphate are found. Mucus 

 is also found in variable quantity, with desquamated epithelium and a 

 few leucocytes. In addition, recent microscopical researches have 

 shown the presence of spores of yeast and a great variety of bacteria, 

 which latter exist in the feces in great abundance. These organisms 

 probably excite many of the so-called putrefactive changes in the intes- 

 tinal contents, which result in the formation of indol, phenol, skatol, 

 cresol etc. According to Senator, these putrefactive products do not 

 exist in the meconium. The quantity of inorganic salts in the feces is 

 not great. In addition to ammonio-magnesian phosphate, magnesium 

 phosphate, calcium phosphate and a small quantity of iron have been 

 found. The chlorides are either absent or are present only in small 

 quantity. 



Marcet has pretty generally found in the human feces a substance 

 possessing the characters of margaric acid, and volatile fatty acids ; the 

 latter free, however, from butyric acid. He also found a coloring 

 matter, which probably is a modification of bile-pigment. Cystin is 

 mentioned as an occasional constituent. 



In addition to the matters just enumerated, the following substances 

 have been extracted from the normal feces : 



Excretin and Excretoleic Acid. Excretin (C 20 H 36 O) was obtained 

 from the normal feces, by Marcet, in 1854. This substance crystallizes 

 from an ethereal solution in two or three days, in the form of long silky 

 crystals. Examined with the microscope, these are found to consist of 

 acicular, four-sided prisms of variable size. Excretin is insoluble in 



