36 STAINING METHODS. 



glass rod. The cover glass is now moved about in the air to promote 

 rapid evaporation of the alcohol, and is then placed in water. The 

 section now remains attached to the cover glass during subsequent 

 manipulations. The aceton-celloidin solution referred to is pre- 

 pared by adding celloidin in small, dry pieces to aceton until a con- 

 centrated solution is obtained. A large drop of this added to five 

 cubic centimetres of absolute alcohol makes a suitable solution for 

 use. This must be kept in a glass-stoppered bottle, and will require 

 to be frequently renewed, as it is not suitable for use after having 

 absorbed moisture from the air. The aceton as obtained from dealers 

 contains considerable water and must be dehydrated by adding to it 

 red-hot sulphate of copper. 



The sections, attached to a slide or cover glass by one of the 

 methods mentioned, are stained with Kiihne's carbol-methylene-blue 

 solution, which is dropped upon them from a pipette. Usually they 

 will be sufficiently stained at the end of half a minute to a minute, 

 but in some cases a longer time and the application of heat will be de- 

 sirable. They are then washed in water and immediately placed in 

 fifty-per-cent alcohol, where they remain until the sections have a 

 pale-blue color with a greenish tinge. They are now completely 

 dehydrated in absolute alcohol and subsequently cleared up in xylol. 



STAINING SECTIONS OP GELATIN STICK CULTURES. Fischl, Wei- 

 gert, and Neisser have given an account of methods for staining 

 stick cultures in gelatin of non-liquefying bacteria. The object of 

 this is to show the mode of growth and the association of individual 

 cells in undisturbed cultures. Neisser gives the following direc- 

 tions : The gelatin cultures are inoculated, by several punctures, 

 with the microorganism to be studied. When the development is 

 deemed sufficient the cylinder of gelatin is removed from the test 

 tube by gently warming its walls. It is then placed for several days 

 one to eight, according to its size and thickness in a one-per-cent 

 solution of bichromate of potassium. While in this solution it must 

 be exposed to the light, which causes a change in the gelatin, ren- 

 dering it insoluble. The gelatin cylinder is thoroughly washed and 

 then hardened in alcohol, first of seventy per cent and then of ninety- 

 six per cent. It is then cut into suitable pieces, and these are attached 

 to a cork in the usual manner and placed for twenty-four hours in ab- 

 solute alcohol. Thin sections may now be made with a microtome, 

 and these are attached to a glass slide and stained by Gram's or 

 Weigert's method or by the use of Loffler's solution (No. 4). 

 The decolorization should be effected by the use of alcohol and not 

 with an acid solution. When Gram's method is used decolorize by 

 the alternate use of alcohol and oil of cloves. Clear the preparation 

 with oil of bergamot. 



