Morphology 493 



baum,* however, that we are indebted for the discovery of 

 the relation which the organism bears to pneumonia. 



Distribution. The pneumococcus is one of a group of 

 widely disseminated organisms of the respiratory tract. It 

 is characterized by certain peculiarities of morphology, 

 certain metabolic peculiarities, a definite pathogenesis, and 

 a distinct agglutinative reaction with immune serum. 

 From such typical individuals a number of irregular depart- 

 ures are known, and recent researches make it certain that 

 many of the organisms formerly looked upon as pneumococci 

 are different and perhaps harmless. The pneumococcus 

 is a purely parasitic, pathogenic organism, best known to 

 us in its relation to croupous pneumonia, where it is present 

 in the lungs, sputum, and blood. It may be found in the 

 saliva of a large number of healthy persons, Parke and 

 Williams, f especially during the winter months, Longcope 

 and Fox, J and the inoculation of human saliva into rabbits 

 frequently causes septicemia in which the pneumococci are 

 abundant in the blood and tissues. Its frequent occurrence 

 in the saliva led Flugge to describe it as Bacillus septicus 

 sputigenus. It is occasionally found in inflammatory lesions 

 other than pneumonia, as will be pointed out below. 



Morphology. The organism is variable in morphology. 

 When grown in bouillon it appears oval, has a pronounced 

 disposition to occur in pairs, and not infrequently forms 

 chains of five or six members, so that some have been dis- 

 posed to look upon it as a streptococcus (Gamaleia) . In the 

 fibrinous exudate from croupous pneumonia, in the rusty 

 sputum, and in the blood of rabbits and mice containing 

 them, the organisms occur in pairs, have a lanceolate shape, 

 the pointed ends usually being approximated, and are 

 usually surrounded by a distinct halo or capsule of clear, 

 colorless, homogeneous material, thought by some to be a 

 swollen cell- wall, by others a mucus-like secretion given off 

 by the cells. When grown in culture-media, especially 

 upon solid media, the capsules are not apparent. The 

 elongate form has led Migula to describe it under the name 

 Bacterium pneumoniae. 



The organism measures about i ^ in greatest diameter, 



* "Wiener med. Jahrbuch," 1886, p. 483. 



t "Jour. Exp. Med.," vn, Aug. 7, 1905, p. 403. 



t Ibid., p. 430. 



"System der Bakterien," Jena, 1900, p. 347. 



