This section is from the book "Diseases Of The Intestines", by Max Einhorn. Also available from Amazon: Diseases Of The Intestines A Text-Book For Practitioners And Students Of Medicine.
The presence of neutral fat and fatty acids is determined in the following manner: The faeces are treated with a considerable amount of ether; the latter is separated and evaporated in a water bath. The fat if present then remains and is visible. In order to show the presence of soaps which do not dissolve in ether, another portion of fecal matter is flirst treated with acids which split up the soaps and then extracted with ether. The quantitative determination of the amount of fat and of its different components is somewhat complicated and of not much service clinically. Those interested in the subject may look up Yon Noorden's "Beitrage zur Lehre vom Stoffwechsel," Heft I., p. 109, Berlin, 1892. Normally fat is never perceptible macroscopically in the faeces unless after the ingestion of very large quantities. It may then be visible in small portions of pea size. Pathologically fat may exist in very large quantities in the fecal matter and give it a grayish silvery appearance, the so-called fatty stools.
This normally occurs in diseases of the pancreas, and also whenever the absorption by the lymphatics is greatly disturbed.
1 S. Basch- "Welche klinische Bedeutung bezeichnetdieSchmidt'sche Gahnmgsprobe der Faeces?" Zeitsckrift f. klin. Med., Bd. 37, Heft 5 and 6.
Fresh blood from the lower portion of the intestine, and also from the higher portions of the bowel if present in large amount, is easily recognized by its macroscopic appearance. Often the microscope will reveal well-preserved red and white blood corpuscles. Sometimes, however, the blood is changed to such a degree that it is not easily recognized. Here various tests are required in order to prove its existence, the same procedures being used as for the discovery of blood in the gastric contents. The haemiu test which is chiefly used is made as follows: A small particle especially suspected of containing blood is dried and powdered and a portion of it put on a slide. A trace of sodium chloride is now added and a drop of glacial acetic acid poured over it and thoroughly mixed. A cover-glass is now put over it, the specimen is slowly heated, and after cooling examined with the microscope. The presence of haematin crystals shows that there was blood.
Under normal conditions no unchanged bile pigment is found in the faeces. In catarrhal conditions of the small intestine it has been frequently detected. The presence of bile pigment is ascertained in the following manner: A particle of highly colored fecal matter is brought into contact with a drop of fuming nitric acid. The yellow color usually passes through the various colors of the spectrum - red, violet to green. In some instances a green discoloration appears at once. The test for biliary pigment may also be made as follows: The faeces if liquid are filtered through filter paper, and if not liquid a watery mixture is made and filtered. When the filter paper is dry a few drops of nitric acid are poured on it. The colors just mentioned appear in the form of rings, if bile pigment is present. Still another test is as follows: A small quantity of the fluid dejecta is treated with a concentrated watery solution of sublimate. If the faeces contain biliary pigments in considerable quantity, the entire mixture turns green.
If, however, the biliary pigment is adherent to certain small fecal particles then these alone turn green.