. Pathological technique; a practical manual for workers in pathological histology and bacteriology. h in water. 5. Cover with sodium sulphid solution ten seconds. 6. Wash in water. This process is gone through with three times. Followingthis the osmic acid solution is applied for thirty seconds, andthe specimen is then washed in water, dried, and mounted inbalsam. A thorough washing in running water is essentialafter the application of each solution to prevent the forma-tion of excessive precipitates. ANIMAL PARASITES. 401 The osmic acid, the first time applied, acts as a fixative anda mordan
. Pathological technique; a practical manual for workers in pathological histology and bacteriology. h in water. 5. Cover with sodium sulphid solution ten seconds. 6. Wash in water. This process is gone through with three times. Followingthis the osmic acid solution is applied for thirty seconds, andthe specimen is then washed in water, dried, and mounted inbalsam. A thorough washing in running water is essentialafter the application of each solution to prevent the forma-tion of excessive precipitates. ANIMAL PARASITES. 401 The osmic acid, the first time applied, acts as a fixative anda mordant. The lead unites with the albumin to form leadalbuminate, a compound insoluble in water. The sodiumsulphid transforms the lead albuminate into lead sulphid, andcauses the preparation to become stained brown. The osmicacid turns the brown color to black. The spirochetes, bac-teria, and cellular detritus are stained black. 6. India Ink Method ofBum.—Approximately equal partsof the juice from the lesion and of fluid India ink are quicklymixed together on a slide with the aid of a platinum loop,. Fig. 129.—Treponema pallidum; smear preparation from a cutaneous papule;stained by Ghoreyebs method; X 1500 (photo, by L. S. Brown). spread thinly, and allowed to dry thereon. When dry, thepreparation is ready to be examined directly with the oil-immersion objective without covering it with balsam and acover-glass. If the material contains many cellular elementsor detritus, it will be necessary to dilute the ink with preparation should have a brown color. The spiro-chetes and bacteria appear as unstained bodies in a brown toblack background. Some specimens of fluid India ink are said to containspirochete-like bodies, and therefore the ink used should beknown to be free from such. 7. LevaditVs Method for Staining Treponema Pallidum inSections.—1. Pieces of tissue about 1 mm. thick are placedin 10 per cent, formaldehyde for twenty-four hours. 2. Rinse in water and place in
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