Staining 



151 



III. 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 parafl5n and celloidin should be re- 

 moved by appropriate solvents. The sections are immersed in the 

 ordinary aqueous solution of the anilin stain and allowed to re- 

 main about five minutes, next 

 washed in water for several min- 

 utes, then decolorized in 0.5 to 

 I per cent, acetic acid solution. 

 The acid removes the stain from 

 the tissues, but ultimately from 

 the bacteria as well, so that one 

 must watch carefully, and so soon 

 as the color has almost disap- 

 peared from the sections, they 

 must be removed and transferred 

 to absolute alcohol. At this point 

 the process may be interrupted to 

 allow the tissue elements to be 

 countercolored with alum-carmin 

 or any stain not requiring acid 

 for differentiation, after which the sections are dehydrated in 

 absolute alcohol, cleared in xylol, and mounted in Canada balsam. 



The greater number of applications can be made by simply 

 dropping the reagents upon the slide while held in the fingers. 

 Where exposure to the reagents is to be prolonged, the Coplin jar 

 or some more capacious device must be employed. 



Keiffer's Metiiod.— The sections are stained for one-half hour in 

 diluted Ziehl's carbol-fuchsin {q.v.), then transferred to absolute 

 alcohol made feebly acid with acetic acid. The sections must 

 be carefully watched, and so soon as the original, almost black- 

 red color gives place to a red- violet color they are removed to xylol, 

 to be cleared preparatory to mounting in balsam. 



Loffler's Method. — Certain bacteria that do not permit ready 

 penetration by the dye require some more intense stain. One of 

 the best of these is Loffler's alkaline methyl ene-blue: 



C/IOSS-SECTION 



SHOWING simes 



IN POSITION. 



Fig. 34. — Coplin's staining jar. 



Saturated alcoholic solution of methylene-blue 30 



I : 10,000 aqueous solution of caustic potash: 100 



*Flugge's "Die Mikroorganismen," vol. i, page S34- 



