6 JOURNAL OF THE [January, 



such minute bodies as the bacteria, before evaporation, but must 

 be evaporated with the drop on the cover, the results of such con- 

 centration of each fixative must be considered in determining its 

 value. The following were found to be efficient in killing instan- 

 taneously and as fixatives, but were all objectionable in that their 

 intermixture with the bacteria in the form of crystalline tufts or 

 flakes, by concentration during the evaporation of the drop, 

 seemed to lessen the adherence of the film, which separated in 

 spots during subsequent processes of the preparation : viz., so- 

 dium chloride, iron sulphate, iodine in solution of potassium 

 iodide, chloral hydrate, quinine sulphate, morphia sulphate, hy- 

 droxylamin, Loefifler's mordant, and fuchsin solution. Of these 

 sodium chloride was the simplest, and often quite efficient. Os- 

 mic acid, picric acid, ether, and chloroform were more satisfac- 

 tory, but especially absolute alcohol, though this last reagent was 

 objectionable on account of the violent currents produced on its 

 addition in a droplet. The best results were obtained with hot 

 water, tannin, chromic acid (in water solution, diluted until color- 

 less by daylight), and hydrogen peroxide. 



As to the staining process, that of Loeffler, with two solutions, 

 mordant and colorant, though specially devised for the staining 

 of cilia, appears well adapted for the staining of the entire bac- 

 terium. However, in place of the unstable salt, iron sulphate, 

 recommended in his formula, it seems better to use, as suggested 

 by L. Luksch,' a cold saturated solution of ferric acetate, with 

 addition of a few drops of acetic acid. The further addition to 

 the mordant — on which Loeffler lays so much stress — of a few 

 drops of solution of sodium hydrate or of hydrochloric acid, ac- 

 cording to the alkaline or acid reactions of the natural products 

 of growth of the bacterium which is to be stained, has been found 

 unnecessary by M. Nicolle and V. Morax.^ With this my own 

 experience coincides ; no actual change of reaction is produced 

 in the mordant, nor any improvement in the results ; the variable 

 and uncertain staining of cilia, often observed, seems to be 

 dependent on quite other conditions, probably connected with 

 the anterior drying of the film. The two solutions as simplified 



1 Ceitralbl. f. Bakt. u. Par., xii. (i8g2\ 430. 



2 Ann. de I'lnst. Past., vii. (1893), 554. 



