DIGESTION. 691 



with water, filter, and evaporate filtrate to a small volume. Test the liquid for 

 sugar with Fehling's solution, and for dextrin and starch with iodine. 



g. Blood. When the blood in the feces is derived from the lower portion 

 of the intestine the red color is so characteristic that further examination is 

 unnecessary. When the blood comes from the upper intestine and the pig- 

 ment has been altered, it becomes necessary to make a spectroscopic examina- 

 tion or the ha3min test, for which see page 658. For the spectroscopic exami- 

 nation, the feces are extracted with water containing a little acetic acid, and 

 the liquid is extracted with ether. If blood is present, the ethereal solution 

 is brownish red. Evaporate the solution to dryness and dissolve the residue in 

 water containing a little sodium hydroxide. The solution is haematin in alka- 

 line solution, and will show the characteristic bands, Fig. 72, e. Hrematin may 

 occur in feces physiologically as a result of a meat diet ; pathologically, it is' 

 found after hemorrhage into the intestine from any source. 



Occult blood is the name given to traces of blood occurring in the feces after 

 small hemorrhages from ulcer of the stomach or duodenum. Its presence is 

 shown as follows : Extract 10 grammes of feces with 25 c.c. of ether to remove 

 fat. To the residue add 5 c.c. of glacial acetic acid and then extract again 

 with 20 c.c. of ether. To this ethereal extract add a little powdered guaiac 

 and then 1 or 2 c.c. ozonized turpentine. A blue color develops on shaking 

 and standing, rendered more intense by the addition of chloroform. 



Klunge's aloin test may be used in place of the guaiac reaction. Mix the 

 acetic acid and ether extract of feces, obtained as above, with 1 or 2 c.c. of tur- 

 pentine, and add immediately about 1 c.c. of a 2 per cent, solution of aloin in 

 70 per cent, alcohol. In the presence of blood the fluid rapidly becomes bright 

 red in color. 



h. Bile-pigments. Shake the feces with a saturated solution of mercuric 

 chloride, filter, and add chloroform. A rose color develops at the junction of 

 the fluids in the presence of urobilin, which is the normal bile-pigment of 

 feces. (The absence of bile-pigment in the feces indicates disease of the liver 

 or obstruction to the flow of bile.) 



Extract feces with chloroform, and to the chloroform solution apply Gmelin's 

 test for bile-pigments. (The presence of bilirubin or biliverdin in the stools 

 of adults indicates catarrh of the intestine.) 



i. Bile acids. Extract feces with alcohol and evaporate the filtrate to dryness. 

 Dissolve the residue in water containing a little sodium hydroxide, and to the 

 solution apply Pettenkofer's test. (Normally, bile acids are completely absorbed, 

 therefore their presence in feces is pathological.) 



j. Ferments. Extract the feces with glycerin, precipitate the solution with 

 alcohol, and dissolve the precipitate in water. To part of the solution add a 

 little starch paste, keep the mixture at 40 C. (104 F.) for several hours, and 

 test for glucose. A positive test indicates the presence of diastatic enzyme. 

 Digest another portion of the solution at the stated temperature with coagu- 

 lated protein and a little sodium carbonate. Filter and apply the biuret 

 reaction, which, if positive, indicates the presence of proteolytic ferment. 

 (The various digestive enzymes are found in the feces when there is diarrhoea 

 resulting from inflammation of the upper intestine.) 



Jc. Inorganic constituents are determined in the usual manner after drying and 

 incinerating the feces. Present are chiefly earthy phosphates, silica, sodium 

 chloride and sulphate, iron compounds, etc. 



