THE PNEUMOCOCCUS 



283 



in artificial media which do not contain albuminous fluids are not 

 encapsulated, and the distinctive lanceolate shape is frequently lost; 

 the organisms become more nearly oval or spherical in outline, but 

 the tendency to remain adherent in pairs is usually maintained. Chains 

 of from four to eight elements are developed in broth cultures, which 

 has led many observers to include the pneumococcus in the strepto- 

 coccus group. The size of the organisms varies considerably; ordi- 

 narily the lesser diameter measures from 0.5 to 0.8 microns, and the 

 longer diameter from 1 to 1.3 microns. 



The pneumococcus is non-motile and possesses no flagella. The 

 capsule, which surrounds pairs of organisms derived from sputum, 

 tissue, body fluids and exudates of man and animals, as well as those 



FIG. 37. Pneumococcus showing capsules. 



cultivated in milk or media containing uncoagulated albuminous sub- 

 stances, is readily demonstrated by the methods of Welch, 1 Hiss 2 and 

 Rosenow. 3 The capsule is poorly formed or absent from pneumo- 

 cocci derived from chronic processes or from mucous surfaces where 

 the organisms are growing as parasites or "opportunists." 



The ordinary anilin dyes stain pneumococci readily, and they are 

 Gram-positive when freshly isolated, but tend to become Gram- 

 negative during cultivation in artificial media. 



Isolation and Culture. Pneumococci grow slowly and feebly upon 

 ordinary laboratory media, and they soon perish. Cultures may 

 be obtained from the blood stream in a large percentage of cases from 

 the fifth day of the disease to the crisis 4 by inoculating 5 to 10 c.c. of 



1 Bull. Johns Hopkins Hospital, 1892, xiii, 128. 



2 Cent. f. Bakt., Ref., 1902, xxxi, 302. 



3 Jour. Infec. Dis., 1911, ix, 1. 



4 Rosenow, Jour. Inf. Dis., 1904, i, 280, 



