CHAPTER IX 



PNEUMOCOCCUS 



(Diplococcus lanceolatus) 



.The pneumococcus occurs in the nose and mouth of many healthy people, 

 and in sputum from those who harbor the organism. 



Morphology . Pneumococci occur chiefly in pairs; they are not, as a rule, 

 spherical, but lancet-shaped, one end oval the other slightly pointed; they are 

 arranged with the long axis of each pair of cocci on the same pole, the oval 

 ends in apposition, the pointed ends at the extremities of the long axis of each 

 pair. Each pair of pneumococci is surrounded by a capsule when they are 



FIG. 14. PNEUMOCOCCUS, FROM CULTURE. SHOWING IN PAIRS AND ALSO A FEW CHAINS; 

 CAPSULESjUNSTAiNED. (4 X eyepiece and y\-i oil immersion objective.) 



found in the body fluids; cultivated upon culture media, the capsule is nearly 

 always lost. This capsule which surrounds each pair of cocci appears as a light 

 halo surrounding the organisms stained in the ordinary way (with Loeffler's 

 methylene blue, eosin, fuchsin or by Gram's); by special methods of staining 

 the capsule may be tinted. 



Pneumococci may be found in chains, but their nature is usually discernible 

 because there is usually a greater distance between each pair than between the 

 elements of pairs, the diplococcic nature remaining apparent. Occasionally 

 pneumococci are oval or almost spherical. Different strains vary in size, the 

 average being slightly larger than staphylococci or streptococci. The pneumo- 



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