r.] MICROSCOPIC EXAMINATION. . 7 



below), then washed for a few seconds with a 10 per cent, 

 solution of nitric acid, then for a few minutes with distilled 

 water. After this the preparation is stained with methyl- 

 blue in the ordinary way. Or, after Koch's method, the 

 specimen is first stained in alkaline methyl-blue (mixed with 

 a 10 per cent, solution of caustic potash) for twenty-four 

 hours, or for half an hour to one hour at a temperature of 

 40 C., and then stained in a concentrated solution of vesuvin. 

 Wash it next with water, then with alcohol, dry, and mount 

 in Canada-balsam solution. 



In leprosy, the specimen on the glass is stained with 

 magenta, then washed in distilled water, then stained with 

 methyl-blue, washed, and mounted. With such organ- 

 isms as e.g. the micrococcus in the sputum of acute croupous 

 pneumonia, and the micrococcus in gonorrhoeal discharge 

 the staining is best carried out with a mixture of methyl-blue 

 and vesuvin. 



Weigert's double stain is very excellent for many purposes ; 

 it is prepared thus : 



Saturated watery solution of aniline, 100 ccm. 



[This is made thus : Aniline oil, 1 part, dist. water, 3 

 parts. Shake every half hour for four hours, and decant the 

 water as the oil settles to the bottom.] 



Saturated alcoholic solution of fuchsin, 11 ccm. Mix. 



The sections are well stained in this mixture, then washed 

 in distilled water ; after this they are immersed for a few 

 seconds in alcohol, and then transferred for one, two, or three 

 hours to the following solution [Watson Cheyne, Practitioner, 

 April 1883, p. 258] : 



Distilled water, 100 ccm. 



Saturated alcoholic solution of methyl -blue, 20 ccm. 



Formic acid, 10 minims. 



After this, wash in alcohol, pass through clove-oil, and mount 

 in Canada-balsam solution. 



In examining fresh or hardened tissues for micro-organisms 

 it is necessary to make thin sections, which can be easily done 

 with the aid of any of the microtomes in common use, 

 amongst which Williams's microtome, and especially Dr. Roy's 

 ether-spray freezing microtome, are no doubt the best and 

 easiest to manipulate. As regards hardened material, it is 

 necessary to remember that the hardening must be carried 



