THE PXEUMOCOCCUS 317 
with sputum, the etiological relationship of the organism to lobar 
pneumonia was not established until 188(), when FrankeP and Weich- 
selbaum- ])ublished their respective studies upon lobar pneumonia. 
Morphology.— Mewed 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 lance- 
olate 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 pairefl arrangement is maintained 
when the organisms remain adherent to form short chains. Cultures 
in artificial media which do not contain alliuminous fluids are not 
Fig. 41. — Pneumococcus mucosus showing capsule. X 1000. 
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 de^'eloped in broth cultures, 
which has led many observers to include the pneumococcus in the 
streptococcus group. The size of the organisms varies considerably. 
Ordinarily the lesser diameter measures from 0.5 to 0.8 micron, 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 
culti\'ated in milk or media containing uncoagulated albuminous 
substances, is readily demonstrated by the methods of Welch,^ Hiss'* 
' Ztschr. f. klin. Med., 1886. 10, 401. Ibid., 1886, 11, 4.37. 
2 Wien. med. .Jahrb., 1886, n. f. I, p. 4S.S. 
■'• Bull. .Johns Hopkins Hosp., 1892, 3, 125. 
* Centralbl. f. Bakteriol., Ref., 1902, 31, 302. 
