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.
In order to ascertain the existence of ferments in the faeces a glycerin extract of them may be made or the fecal matter may be directly mixed with water containing a small proportion of thymol, and filtered. The filtrate, or the glycerin extract, can now be directly tested for the presence or absence of the different ferments, trypsin and diastase. In order to test for trypsin the fecal filtrate is made alkaline by the addition of bicarbonate of sodium and a few flakes of fibrin are added. The solution is kept at blood temperature for a few hours and then tested with potassium hydrate and a weak solution of sulphate of copper. If trypsin is present, a pinkish-red color will arise in consequence of the peptone which has formed (biuret test). In order to test for diastase, a few cubic centimetres of the filtrate are mixed with about half the amount of a starch solution and kept at blood temperature for half an hour. The mixture is now subjected to Fehling's or Trommer's test for the presence of sugar.
Normally, as a rule, these ferments are absent, but in pathological conditions, especially in diarrhoea, they are frequently found.
The faeces occasionally contain concretions which may be of diagnostic importance. In order to detect them, especially if they are small, the faeces must be thoroughly mixed with warm water ami poured through a large sieve. While the fecal matter is on the sieve some more water is added and the mass constantly stirred with a wooden stick. Any concretions present will thus be discovered remaining on the surface of the sieve.
1 Bunge: "Lebrbuch der phys. u. pathol. Chemie, " Leipsic, 1887, p. 192.
Biliary calculi are easily recognized when they attain considerable size. When they are very small, however, their recognition is somewhat more difficult. The principal constituents of biliary calculi are cholesterin and bile pigment in conjunction with lime.
The small concretions (sand) suspected to be of biliary origin should be examined in the following way: About 2 gm. of the mass is well powdered and treated with 20 c.c. of ether, thoroughly mixed and filtered, the filtrate evaporated and tested for the presence of cholesterin in the following manner: (a) Part of the residue is dissolved in hot alcohol and put aside on a porcelain dish for spontaneous evaporation. The precipitate is examined under the microscope. Crystals of rhomboid shape with a ragged edge are characteristic of cholesterin. (b) Another portion of the residue is directly put on a slide, a drop of concentrated sulphuric acid added, and covered with a cover-glass. The cholesterin crystals assume a carmine color at their margins. If now a drop of Lugol's solution is added a violet color arises, (c) Another portion of the residue is treated with hydrochloric acid and a trace of chloride of iron and evaporated. If cholesterin is present a blue color arises. The residue of the original ether mixture is treated with diluted hydrochloric acid, heated, and extracted with chloroform after it has cooled off.
The chloroform extract is now tested with Mellin's reaction (fuming nitric acid). The presence of bile pigment produces the well-known change of colors.