512 BACTERIOLOGY. 



and as obtained from the saliva it differs again 

 from the organism when occurring in pneumonia. 

 When grown on artificial culture media, variations in its 

 morphology have been observed, at one time the indi- 

 vidual cells being oval in shape and united in pairs, and 

 then surrounded by a capsule; at other times spherical 

 and arranged in longer or shorter chains, like strepto- 

 cocci, and then being without a capsule. Variations 

 in virulence have also been noted, both in the animal 

 body in different stages of disease and when grown out- 

 side the body on artificial culture media. These great 

 variations in biological and pathogenic properties have 

 induced some investigators to believe that there were 

 several distinct species of this organism. 



These views, however, have not met with general 

 acceptance. In an exhaustive investigation into the 

 subject by Kruse and Pansini, who obtained the micro- 

 cocci from the most varied sources from the saliva in 

 health and disease, from the nasal secretions, from pneu- 

 monic sputum at different periods and phases of the 

 illness, from the blood of different kinds of animals 

 killed by inoculation, and, finally, from many primary 

 and secondary affections due to this organism after 

 carefully weighing their results from different points 

 of view and comparing the morphological, biological, 

 and pathological characteristics of the various micro- 

 cocci found, these observers have come to the conclu- 

 sion that "it is impossible to distinguish different 

 varieties" of pneumococci. They found numerous 

 quantitative and qualitative variations in virulence, 

 growth, power of resistance, etc., but at the same time 

 such an inconstancy in these variations that they were 

 unable to make any classification into separate varieties. 



