MICROSCOPIC AT. TECHXIQFE. -^21 



water into ;^^ per cent, tannic acid solution to decolorise, allowed 

 to remain from two to five minutes, then rinsed with water to 

 enable the exact tint to be observed more readily. If satisfactory, 

 after a thorough washing with water, the sections are placed in 

 absolute alcohol, or a solution of gold in the same if a yellow 

 counter stain be desired, cleared in oil of bergamot, and mounted 

 in balsam. If the excess of stain is not readily removed, a few 

 minutes' immersion in 25 per cent, nitric acid, followed by dilute 

 spirit, water, and absolute alcohol respectively, will effect its 

 removal By adopting this method it is said to be possible to 

 distinguish two kinds of nuclei (voilet and blue), the fibrine, and 

 the protoplasm of the plasma-cells. The bacilli stain red, whilst 

 the mucus surrounding them is blue, and the organisms are said to 

 appear in their natural character, " in fish-roe like masses of 

 vegetable mucus.'' It is claimed that the process is particularly 

 suitable for use in the study of leprosy. It appears to depend 

 upon the property, also utilised by NicoUe, by which tannin con- 

 verts methylene blue into an insoluble form. — S/ieff. Med. Journ.^ 

 I., 177. 



Staining Reactions of Leucocytes.^— Wright and Bruce show 

 that both " oxyphile " and " basophile " elements, according to 

 Ehrlich's classification, attracting acid and basic dyes respectively, 

 exist in leucocytes. The nucleus is invariably basophile, thus 

 resembling cell nuclei generally, whilst the granules found in the 

 leucocytes of the normal circulating blood in mammals are 

 oxyphile. For complete histological differentiation, the two kinds 

 of elements must be brought out in relief, and the following 

 method of staining is suggested as satisfying the theoretical require- 

 ments. After fixing the cover-glass specimens of blood by dry 

 heat or chemical reagents — such as osmic or picrid acid — the 

 oxyphilous elements of the leucocytes are stained by floating the 

 covers as long as may be necessary on a i per cent, aqueous 

 solution of eosin or other acid aniline dye. The basophilous 

 elements are next treated with a basic aniline dye, or with carmine 

 or haematoxylin combined with alum to render them basic. 



Leofller's methylene blue is recommended by the authors, on 

 account of the rapidity of its action. Care must be taken to 



* Phar. Journal. 



International Journal of Microscopy and Natural Science. 



Third Series. Vol. III. x 



