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 microscopical examination of the faeces is occasionally of assistance in establishing the diagnosis. With Ewald 1 I do not think it necessary to examine microscopically the faeces of every patient presenting intestinal symptoms. In cases, however, in which the diagnosis is not quite clear and the symptoms point to an intestinal lesion, a microscopical examination of the faeces should be made.
Diarrhoeal stools may be examined under the microscope without any further preparation. Solid fecal matter is examined by taking a small particle of the faeces, putting it on a slide, and mixing it thoroughly with a drop of physiological salt solution. In order to avoid the unpleasant odor, a small amount of a watery one-per-cent formalin solution may be first added to the fecal matter. The microscopic picture of the normal faeces varies greatly according to the diet. In people living on a meat diet no vegetable residue will be seen, while there will be no remnants of meat in people subsisting on an exclusively vegetable diet. In case of a mixed diet there will be remnants of both in the stool. A mixed diet will reveal the following appearances: There will be a large number of plant cells, the remnants of various vegetables and fruits. They are usually of considerable size, present peculiar shapes, and can be easily differentiated from animal cells (Figs. 16, 17, 18, 19). The peels of pears and apples and of prunes commonly pass out in the stool entirely unchanged. Notwithstanding the presence of these plant cells in the stools starch, as a rule, is absent. Thus the microscopical specimen when stained with Lugol's solution will show no blue color.
If, however, starch appears in a stool in well-preserved granules, it is always pathological, indicating deficient digestion. Minute fragments of meat are found in small quantity in the stools. Although considerably changed the muscles can be recognized as such, and the transverse markings can often be noticed. Frequently they present a yellowish tinge from biliary pigment. Connective-tissue fibres and also elastic fibres are occasionally met with, both being quite resistant to the action of the digestive juices. The presence of numerous pieces of meat in the stool is pathological. Fat. - Microscopically fat can be detected in the feces in the form of colorless small globules which may exist in 5 large numbers after an excessive milk diet or in the shape of small needle-shaped crystals, or again in the form of sheaves. The small crystals of needle shape usually occur singly, and consist mostly of fatty acids, while the sheaves consist of fatty soaps. The fatty-acid crystals melt and disappear when heated, while the soaps remain unchanged. Ether likewise causes a disappearance of the fatty acids, while the soaps remain unchanged. Rieder 1 suggests the use of the dye stuff Sudan II. (C 22H 10N.O) in a concentrated alcoholic solution for the differentiation of the fats.
This dye stains plain fat bright red, while crystals of fatty acid and of lime and magnesia soaps remain unchanged. While normally these different forms of fat appear in very scanty amounts in the faeces, they may be found considerably increased under pathological conditions (affections of the liver, pancreas, and acute enteritis).
1 C. A. Ewald: "Diseases of the Intestines." Twentieth Century Practice of Medicine, vol. ix.. p. 113.
Fig. 17. - Normal Faeces showing Detritus, Plant Cells, Digested Muscle Fibres, Bacteria.
Fig. 18. - Different Varieties of Vegetable Cells found in Normal Faeces.
FIG. 19. - Stool of an Hysterical Patient who Simulated Passing of Large Quantities of Mucous Membranes in the Faeces. The membranes under the microscope showed the structure of common tissue paper; a few plant cells, epithelial cells, and fat crystals were also present.