Staining 465 



blood of rabbits and mice, and in albuminous liquids generally, 

 the organisms occur in pairs, have a lanceolate shape, the pointed 

 ends usually being approximated, and are usually surrounded by a 

 distinct halo or capsule of clear, colorless, homogeneous material, 

 thought by some to be a swollen cell-wall, by others a mucus-like 

 secretion given off by the cells. When grown in fluid culture media 

 without albumin, it appears more rounded, lacks the capsule and 

 though it has a pronounced disposition to occur in pairs, not in- 

 frequently forms chains of five to six members, so that some have 

 been disposed to look upon it as a streptococcus (Gamaleia). When 

 grown upon solid media, the capsules are not apparent. The 

 lanceolate form led Migula* to describe it under the name Bacterium 

 pneumoniae. 



The organism measures about i m in greatest diameter, is without 

 motility, has no flagella and forms no spores. 



Staining. — It stains well with the ordinary solutions of the anilin 

 dyes, and gives most beautiful pictures in blood and tissues when 

 stained by Gram's and Weigert's methods. Dead pneumococci are 

 commonly Gram-negative. 



To demonstrate the capsules, the glacial acetic acid method of 

 Welchf may be used. The cover-glass is spread with a thin film of 

 the material to be examined, which is dried and fixed as usual. 

 Glacial acetic acid is dropped upon, it for an instant, poured (not 

 washed) off, and at once followed by anilin-water gentian violet, in 

 which the staining continues several minutes, the stain being poured 

 off and replaced several times until the acid has all been removed. 



Finally, the preparation is washed in water containing i or 2 per 

 cent, of sodium chlorid, and may be examined at once in the salt 

 solution, or mounted in balsam after drying. The capsules are more 

 distinct when the examination is made in water. 



Hiss I recommended the following as an excellent method of stain- 

 ing the capsules of the pneumococcus : The organism is first culti- 

 vated upon ascites serum-agar to which i per cent, of glucose is 

 added. The drop containing the bacteria to be stained is spread 

 upon a cover-glass mixed with a drop of serum or a drop of the fluid 

 culture-medium, and dried and fixed. A half-saturated aqueous 

 Solution of gentian violet is applied for a few seconds and then washed 

 off in a 25 per cent, solution of carbonate of magnesium. The 

 preparation is then mounted in a drop of the latter solution and 

 examined. 



If it is desired to stain the capsules and preserve the specimens 

 permanently in balsam. Hiss employed a 5 or 10 per cent, solution 

 of fuchsin or gentian violet (5 cc. saturated alcoholic solution of 



*" System der Bakterien," Jena, igoo, p. 347. 

 . t"Bull. of the Johns Hopkins Hospital," Dec, 1892, p. 128. 



t Abstract, "Centralbl. f. Bakt. u. Parasitenk.," Bd. xxxi, No. 10, p. 302, 

 March 24, 1902. More complete details appear in a later paper in the "Journal 

 of Experimental Medicine," vi, p. 338. 

 30 ■ 



