386 INFECTIVE DISEASES. 



must be left in it for an hour. Sections are treated on the same 

 principles, but must be left in the solution for several hours. The 

 crumpling of the sections by the action of nitric acid is avoided. 



Baumgarten's method. Cover-glass preparations of sputum are made 

 as already described, and immersed in a very dilute solution of potash 

 (1 to 2 drops of a 33 per cent, solution of potash in a watch-glass of dis- 

 tilled water). The cover-glass is pressed down on a slide, and examined 

 with a high power. The bacilli can be thus examined in the unstained 

 condition, and to avoid any mistake from confusion with other species, 

 the cover-glass can be removed, dried, passed through the flame, and 

 stained with a drop of an aqueous solution of fuchsine, or gentian- violet. 

 The putrefactive bacteria are stained, but the tubercle bacilli remain 

 absolutely colourless. 



Baumgarten's new method. A. solution is prepared as follows : Drop 

 4 to 5 drops of concentrated alcoholic methyl-violet solution into a small 

 watch-glass full of water, (a) Stain the sections in this solution, wash 

 them in water, and decolorise in absolute alcohol (five to ten minutes) ; 

 or, before treating with alcohol, immerse the sections for five minutes in 

 a half -saturated solution of carbonate of potash. Pass through clove-oil, 

 and mount in a mixture of Canada balsam, free from chloroform, and 

 clove-oil (equal parts). The object of this process is to differentiate the 

 tubercle bacilli from chance bacteria, inasmuch as the tubercle bacilli 

 are gradually decolorised by the clove-oil. (Z>) Sections stained in the 

 above solution are placed for five minutes in alcohol, and then in a 

 concentrated solution of Bismarck-brown in 1 per cent, solution of acetic 

 acid. The after-treatment may be conducted as already described. 



Ziehl-Neelsen method. Cover-glass preparations may be quickly stained 

 in Neelsen's solution warmed in a watch-glass till steam rises. Sections 

 are left for from five to ten minutes in the solution, and then washed in a 

 watery solution of sulphuric acid (25 per cent.), rinsed in distilled water, 

 and immersed in methylene-blue solution. After two or three minutes 

 they are passed through alcohol and oil of cloves, and mounted in Canada 

 balsam. 



FranlceVs method. Sputum preparations are rapidly double-stained 

 by the following method : Prepare a solution by adding concentrated 

 alcoholic methyl-violet or fuchsine solution, drop by drop, till opalescence 

 arises, to 5 com. of aniline- water heated to 100 C. Float the prepared 

 cover-glasses two minutes in the warmed solution. The process of after- 

 staining and decolorisation is effected by placing the preparation for one 

 to two minutes in one of the following solutions : for fuchsine-stained 

 preparations, a saturated solution of methylene-blue in a mixture of 



Alcohol 50 



Distilled water .30 



Nitric acid 20 



which is filtered before use ; for preparations stained in methyl- violet, a 

 saturated solution of vesuvin may be used in 



Alcohol .70 



Nitric acid . 30 



