282 STREPTOCOCCUS-PNEUMOCOCCUS CROUP 



by serological and pathological methods, and that these types were 

 mutually stable, for long-continued passage through animals failed 

 to alter or modify their general cultural and agglutinating properties, 

 although the virulence of the respective types for one or another 

 animal could be increased or decreased. It is not improbable that a 

 thorough study of the streptococcus group may reveal similar sero- 

 logical variance and that in the type now designated Streptococcus 

 pyogenes several individual types parallel to those of the pneumococcus 

 may be demonstrated. 



The important question for the moment is, do these changes of 

 virulence, et cetera, exhibited by the streptococcus influence the diag- 

 nostic aspect of the question? Theobald Smith has admirably summed 

 up the present status of the subject in the following words : " Spon- 

 taneous changes in the cultural characters of the streptococcus do not 

 proceed rapidly enough, if they go on at all, to interfere with current 

 bacteriological methods. Tendencies toward slow changes may be 

 used as further valuable distinguishing characters." 1 



THE PNEUMOCOCCUS. 



Synonyms. Micrococcus pasteuri, Diplococcus pneumonia, Diplo- 

 coccus lanceolatus, Streptococcus lanceolatus. 



Historical. Although the pneumococcus was observed by Stern- 

 berg 2 and independently by Pasteur 3 in the blood of rabbits inoculated 

 with sputum, the etiological relationship of the organism to lobar 

 pneumonia was not established until 1886, when Frankel 4 and Weich- 

 selbaum 5 published their respective studies upon lobar pneumonia. 



Morphology. Viewed under the microscope, the pneumococcus 

 presents two distinct appearances, depending upon the source of the 

 culture. Observed in human or animal tissues, exudates or body 

 fluids, or in media containing non-coagulated albuminous fluids, as 

 blood serum, ascitic or hydrocele fluids, the organisms occur typically 

 in pairs surrounded by a definite capsule, or less commonly in short 

 chains enclosed in a capsule. The individual cells are typically lanceo- 

 late in shape with the apposed surfaces of each pair flattened, and the 

 distal ends somewhat pointed. Less commonly the organisms are 

 oval, or nearly spherical. The paired arrangement is maintained 

 when the organisms remain adherent to form short chains. Cultures 



1 Smith and Brown, Jour. Med. Research, 1914, xxxi, 501. 



2 National Bureau of Health, 1881. 



3 Compt. rend. Acad. Sci., 1881, xcii, 159. 



4 Zeit. f. klin. Med., 1886, x, 401. Ibid, xi, 437. 

 6 Wien. med. Jahrb., 1886, p. 483. 



