1896.] MICROSCOPICAL JOURNAL 35 



crusts without decolorizing the micro-organisms which they 

 contain, so that is possible to demonstrate the organisms in 

 situ, thus showing their mode of growth, and thus to study the 

 natural cultures of these germs. This method of investigation 

 is particularly adapted to such diseases as eczema, psoriasis, 

 pityriasis, versicola, eryphema, impetigo, etc. 



The details of the method are as follows ; Place a piece of 

 zinc plaster upon the portion of the skin to be examined, press- 

 ing gently with the hand for a few minutes. When the plaster 

 is removed, a portion of the diseased product will be found ad- 

 hering to it, and with the various structures remaining in their 

 normal relations to each other. A bit of plaster with the speci- 

 men adhering to it may be dried and laid aside for future ex- 

 amination, or may be examined at once, being first placed in a 

 bath of benzine, by which the specimen is separated from the 

 plaster, and, as is floats away, may be easily removed with a 

 few particles of zinc adhering. These are removed by immers- 

 ing the specimen in absolute alcohol acidulated with hydro- 

 chloric acid. When the particles of zinc have been wholly dis- 

 solved, the specimen is transferred to water, in which it swells 

 up and becomes capable of absorbing the coloring matters. 



Placing the specimen upon an object carrier, the particles are 

 first covered with a solution of gentian violet dropped upon it 

 with a glass rod. The gentian violet is made by adding to 

 twenty minims of alcoholic solution of gentian violet ten min- 

 ims of ammoniated lime water. In fifteen or twenty minutes 

 the staining is completed,- when the excess of fluid is removed 

 by means of blotting-paper, and the specimen is dried. 



Next apply a few drops of a solution consisting of equal parts 

 of a five per cent solution of iodine of potash and peroxide of 

 hydrogen for two or three minutes. Dry the section with blot- 

 ting-paper, cover with an aniline mixture, — either picro-aniline 

 or eocene-aniline, and watch the decolorizing process as it 

 slowly progresses. At least two hours will be required to com- 

 plete the decolorization ; a longer time does no harm. If but 

 a small quantity of the acid is added to the aniline mixture, the 

 specimen may with advantage be left in the solution over night. 

 Clear specimens are obtained in this way. Unna recommends 

 the following formulae ; — 



