l894-] NEW-YORK MICROSCOPICAL SOCIETY. 9^ 



over concentrated sulphuric acid within a desiccator, or, still 

 better, in vacuo over sulphuric acid, under an air-pump. 



When thoroughly dry, insert all the covers in the brass wire 

 coil, with film surfaces all directed toward its lower end, and with 

 arranged and noted succession for identification, if different 

 kinds of bacteria are included in the series. With some species 

 it appears desirable to hold the coil a few seconds in a current of 

 warm air to complete the drying. 



Dip the coil for a moment in sterilized water, to dissolve away 

 excess of fixative, remove the water drops by touching absorbent 

 paper, and again dry the covers. 



Hang the coil for one-half to one minute in the flask of 

 mordant, heated nearly to boiling. Remove the co'l and take up 

 excess of mordant by touching absorbent paper ; wash by swing- 

 ing gently, for about five seconds, in a vessel of distilled water, 

 then in solution of acetic acid (20 per cent), again in water, and 

 remove water drops by touching absorbent paper. 



Without drying, hang the coil in the flask of hot colorant for 

 five to sixty seconds, according to depth of staining desired and 

 the readiness of absorbence of the species, determined by trial. 

 Remove the coil, take up excess of stain by touching absorbent 

 paper, and wash as before in another vessel of distilled water. 



Remove the covers from the coil, and lay, film downward, on 

 a soft filter paper. Dry by pressing gently under another filter. 

 Clean the upper face of each cover by rubbing with corner of 

 rag moistened with alcohol, keeping the cover stationary to 

 avoid rubbing away the underlying film. Lay upon a glass slide, 

 remove to stage of microscope, and examine and select the covers 

 preferable for mounting. 



Mount in hardened balsam, or in a saturated solution of potas- 

 sium acetate within a very shallow spun cell of balsam-paraffin, 

 King's cement, or Hollis glue. In cases, delicate details of struc- 

 ture may be best shown by mounting in air — e.g., over a filmy 

 ring of paraffin. 



The fugitive character of staining effected by anilin colors has 

 recently led E. Van Ermengem to devise the following process' 

 of staining the cilia of bacteria, founded on the reduction of 

 silver from a solution of its nitrate. 



1 Ann. de Micrographie, v. (1893), 394- 



