BIOLOGY OF PNEUMOCOCCUS 83 



lander 486 " 7 as a Kapsel, it was later called a rim, or a hull, and 

 its presence undoubtedly contributed to the confusion between the 

 cocci first described by Friedlander and the well-known bacillus 

 that bears his name. Because of the inconstancy of its appearance 

 particularly under different conditions of artificial cultivation, the 

 belief arose that it was not a diagnostic feature of the species. 

 Pane 1045 went so far as to assert that it was a degenerative and not 

 a developmental phenomenon. Friedlander had always contended, 

 however, that the capsule was the product of a vital function of 

 the cell. 



Aoki 18 noticed that capsule formation proceeded more rapidly 

 at body than at lower temperatures, and that the capsules were 

 larger and more distinct when the cocci were grown in immune se- 

 rum or in media containing such serum. This was the Quellung ef- 

 fect utilized by Neufeld and Etinger-Tulczynska 988 in their re- 

 cently published method for type determination. The capsule was 

 often described as gelatinous but, since the time of Pasteur and 

 Friedlander, it had been more generally believed to consist of mu- 

 cin. It was Preisz 1108 who, acting upon this assumption, was the 

 first to demonstrate capsular material in the blood and other body 

 fluids of animals succumbing to pneumococcal infection. He be- 

 lieved that a general, fatal invasion of the body by these cocci 

 could occur only when the accumulation of mucin — now soluble 

 specific substance — in the body had reached a certain level. 



STAINING THE CAPSULE 



Many methods have been devised for demonstrating the capsule 

 of Pneumococcus. The first record of a capsule stain for Pneumo- 

 coccus is that by Friedlander (1885) 491 who, after fixing the prepa- 

 ration in the flame, dipped it for a few minutes in one per cent ace- 

 tic acid. After blowing off the acid he dried and then stained the 

 film by a few seconds' exposure to a saturated aniline-water gen- 

 tian violet solution. MacConkey (1898) 843 recommended staining 

 with dahlia, methyl green, and a saturated alcoholic solution of 



