STAINS 2Q 



dried on the lens, wipe it with a handkerchief just moistened 

 with xylol or pure turpentine, and then wipe quickly with a 

 dry handkerchief. Never dip the point of a lens into xylol or 

 alcohol. Never remove the front combination of an oil- 

 immersion lens for cleaning or any other purpose. 



STAINS 



The following stains are all that is really necessary for the 

 vast majority of purposes : methylene blue, basic fuchsin, 

 gentian violet, neutral red, thionin, and water-soluble eosin. 

 Bismarck brown may also be obtained. Ten grammes of each 

 will last the practitioner for a long time, and this amount 

 costs from 7d. to is. 



They are conveniently kept in a saturated solution of abso- 

 lute alcohol. The following formulae are the most useful : 



1. A Saturated Watery Solution of Methylene Blue. This 

 does not keep very well, and a fresh amount should be pre- 

 pared after a month. It is mostly used for staining blood- 

 films, and for staining wet specimens' of cells from the pleura, 

 pericardium, etc.; borax methylene blue will serve every pur- 

 pose in bacteriological work. Instead of this I now employ 

 acid methylene blue (No. 9). 



2. Loffler's methylene blue is prepared by adding 30 c.c. of a 

 saturated solution of methylene blue (alcoholic) to 100 c.c. of 

 a i in 10,000 solution of caustic potash. 



The potash solution is prepared thus : Take i c.c. of a 10 per 

 cent, solution of caustic potash and make up to 100 c.c. with 

 water ; shake thoroughly and pour away 90 c.c. ; make up to 

 100 c.c. with water, and again shake. A sufficiently close ap- 

 proximation is made by adding i minim of the 10 per cent, 

 solution to 2 ounces of water. 



This stain keeps fairly well. 



3. Hanson's borax methylene blue, which I now use in place 

 of Loffler's blue and find much preferable. A stock, solution 

 (which keeps well) is prepared by dissolving 2 grammes of 

 methylene blue and 5 grammes of borax in 100 c.c. of water. 

 It is to be diluted with five to ten times its volume of water 

 for use. It may be used whenever Loffler's blue is recom- 

 mended. In English measures it is methylene blue, grs. xxx.; 

 borax, grs. Ixxv. ; aq., Biii.ss. 



