Staining 159 



Ninety-five per cent, alcohol, twelve to twenty-four 



hours ; 



Absolute alcohol, six to twelve hours; 

 Chloroform, benzole, or xylol, four hours; 

 A saturated solution of paraffin in one of the above 



reagents, four to eight hours. 



The block is then placed in melted paraffin in an oven 

 or paraffin water-bath, at 5o-6o C., until the volatile 

 reagent is all evaporated, and the tissue impregnated with 

 paraffin (four to twelve hours), and finally embedded in 

 freshly melted paraffin in any convenient mold. In cutting, 

 the knife must be perfectly dry. 



The cut paraffin sections can be placed upon the surface 

 of slightly warmed water to flatten out the wrinkles, and 

 then floated upon a clean slide upon which a film of Meyer's 

 glycerin-albumen (equal parts of glycerin and white of egg 

 thoroughly beaten up and filtered, and preserved with a 

 crystal of thymol) has been spread. After drying, the slides 

 are placed in the paraffin oven for an hour at 60 C., so 

 that the albumen coagulates and fixes the sections to the 

 glass. 



When sections so spread and fixed upon the slide 

 are to be stained, the paraffin must first be dissolved in 

 chloroform, benzole, xylol, oil of turpentine, etc., which 

 in turn must be removed with 95 per cent, alcohol. The 

 further staining, by whatever method desired, is accom- 

 plished by dropping the reagents upon the slide. 



///. Glycerin-gelatin. As the penetration of the tissue 

 by celloidin is attended with deterioration in the staining 

 qualities of the tubercle bacillus, it has been recommended 

 by Kolle * that the tissue be saturated with a mixture of 

 glycerin, i part ; gelatin, 2 parts ; and water, 3 parts ; cemented 

 to a cork or block of wood, hardened in absolute alcohol, 

 and cut as usual for celloidin with a knife wet with alcohol. 



Staining. Simple Method. For ordinary work the 

 following simple method can be recommended: After the 

 sections are cut and cemented to the slide, the paraffin 

 and celloidin should be removed by appropriate solvents. 

 The sections are immersed in the ordinary aqueous solution 

 of the anilin stain and allowed to remain about five minutes, 

 next washed in water for several minutes, then decolorized 

 * Fliigge's " Die Mikroorganismen," vol. i, page 534. 



