The Faeces
It is advisable to examine a stool macroscopically before taking up the microscopical examination. Pus or blood in stools may often be noted without the aid of the microscope.
The normal stool is sausage-shaped and soft.
The mucus of bacillary dysentery is opaque and grayish from the great number of pus and phagocytic cells. It is well to remember that Charcot-Leyden crystals, which are practically always absent from bacillary dysentery stools, are not infrequent findings in the amoebae-containing stools; of course, these crystals appear in other intestinal parasite infections.
In obstruction of the common bile duct we have acholic, whitish, foul-smelling stools. If the putty color be due to bacterial change exposure to the air will restore the brownish tinge.
Sprue stools are whitewash to putty-colored, pultaceous, and filled with air bubbles. The amount is excessive.
A very practical way of obtaining amoebae is to pass a rectal tube or a piece of drainage tube with fenestrations into the bowel, and amoebae may be found in the mucus filling the perforations in the tube.
Ordinarily the stool is best collected in quart fruit jars and examined as soon after evacuation as possible. The wooden spatula-like tongue depressors are well adapted for handling the specimen.
In examining a stool, it is well to color the drop of faeces, which is to be covered with the cover-glass, with a small loopful of ½% solution of neutral red. If diluting fluid is used, it should be salt solution, and not water. The neutral red tinges the granules of the endoplasm of amoebae and flagellates a very striking brown-red color, thus differentiating them from vegetable cells or body cells.
Encysted protozoa are difficult to diagnose, unless one possesses considerable experience. In examining for encysted amoebae as well as for bringing out the number of flagella of flagellates I now use the following method: Take a clean slide and make a vaseline line across it about 1 inch from the end. A drop of the iodine solution is placed on the slide about ½ inch from the vaselined line and a suitable portion of the faeces to be examined is emulsified in it. The edge of a square cover-glass is then applied to the vaselined line and allowed to drop on the preparation. By pressure suitable thicknesses of fluid can be examined. There is an absence of current motion.