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.
According to Hoppe-Seyler, mucin forms one of the principal constituents of the faeces. In order to test for it the faeces are thoroughly mixed with water and an equal volume of milk of lime, allowing the mixture to stand for several hours. It is then filtered. Acetic acid is now added to the filtrate. In the presence of mucin a precipitate forms. In case particles of suspected mucus are visible within the faeces, they can be examined separately in the following manner: A small flake of the mucus is dissolved in a weak solution of potassium or sodium hydrate, and acetic acid added. If the precipitate remains undissolved after the addition of the acetic acid in excess, it proves the presence of mucin. Inasmuch as nucleoalbumin also gives the reaction just described, the positive proof that the precipitate is due to mucin is afforded by heating it in a diluted mineral acid to the boiling-point. If mucin is present the heated solution will contain a substance reducing copper oxide. Another very useful test for the presence of mucin consists in staining the flake of fecal matter resembling mucus with a weak triacid solution (Ehrlich). The presence of mucus pro- duces a green color, while if the flake consists of albumin, a red color arises.
This test, first described by Pariser,1 I have found of practical value.
In order to examine the faeces for albumin, they are treated repeatedly with water slightly acidified with acetic acid. The watery extract is filtered several times and the filtrate examined for albumin according to the methods used in examinations of the urine for this substance. The addition of acetic acid and potassium ferro-cyanide, however, is best suited for this purpose. Under normal conditions there is no albumin present in the faeces.
1 Pariser: Deutsche medicinische Wochenschnft, 1893, No. 41.
Von Jaksch 1 found it present in typhoid fever, in isolated cases of acute enteritis, and in chlorosis.
After the test for albumin has been made with negative result, the watery extract of the faeces is treated with phosphotungstic acid, the precipitate diluted with water and sodium hydrate and a small amount of a weak solution of sulphate of copper added. A purplish-red color (biuret test) shows the presence of both propeptones and peptones. If it is desirable to ascertain the presence of peptones separately it is necessary to first precipitate the propeptone by the addition of a large amount of ammonium sulphate. In normal dejecta Von Jaksch never encountered peptone. Pathologically he found it in typhoid fever, dysentery, tuberculous ulcer of the intestine, and in perforation peritonitis.
In order to test for the presence of carbohydrates, the faeces are subjected to distillation. The residue is extracted with alcohol and ether; the extract is then boiled with water, filtered, and again boiled with the addition of dilute sulphuric acid. This solution is then subjected to Trommer's or Nylander's test for the presence of reducing substances.
In order to ascertain whether starch is present the watery extract of the feces is examined with Lugol's solution, the presence of starch producing a blue color.
If the dejecta be examined for the presence of sugar, then a watery extract of the fecal matter can be directly tested with the usual sugar reagents. Normally neither starch nor its derivatives (sugar) are found.
Schmidt 2 suggested testing the watery extract of the fecal matter with regard to the amount of gas developing through fermentation. For this purpose Schmidt puts the watery extract of the faeces into fermentation tubes (similar to the fermentation saccharometer) and keeps them at blood temperature. The greater the amount of gases developing in the cylindrical part of the tube, the greater the evidence of disturbances within the intestine. The greater proportion of the gas consists of carbonic acid and is due to its formation from the carbohydrates existing in the fecal matter. In order to be able to judge more accurately from this test, Schmidt examined his patients after a certain diet which they had been taking for several days. It consisted of 1,560 c.c. of milk, four eggs, three zwieback, one plate of barley soup, one plate of flour soup, and one cup of bouillon a day. While Schmidt asserts that whenever a considerable amount of gas is found in the fermentation tube this indicates a real disturbance of the intestine, S. Basch,1 who has made a thorough study of Schmidt's method in a considerable number of cases, is of the opinion that on the one hand a considerable amount of gas may be found in cases without any apparent intestinal lesion, and, on the other hand, grave disturbances of the intestine may show a total absence of gas.
Inasmuch as Schmidt's fermentation method is certainly complicated and its results are not of great diagnostic value, I do not believe that it will ever come into practical use.
1 Von Jaksch: " Klinische Diagnostik. "
2 Ad. Schmidt: Berliner klinische Wochenschrift, 1898, No. 41.