56 STUDY AND IDENTIFICATION OF BACTERIA 



also dies out in a few days unless transferred to fresh media. The 

 best medium for its preservation is rabbit's blood agar; this also main- 

 tains the virulence. On this medium the colonies are larger than on 

 agar and they present a greenish appearance. 



The pneumococcus growth emulsifies very readily and evenly so that suspensions 

 for vaccines are easily made. 



It is a well-known fact that the pneumococcus is a frequent inhabitant of the 

 nasal, pharyngeal, and buccal cavities. The explanation of infection is either on 

 the ground of lowered resistance of the patient or enhanced virulence of the organism. 

 Oscar Richardson has reported an organism in cases of lobar pneumonia, cerebro- 

 spinal meningitis, mastoid disease, etc., bearing resemblance to both pneumococci 

 and streptococci the Streptococcus capsulatus. It differs from the pneumococcus 



*** *;. 



*f T*k~i 



* ' ds* 





r 



m.m^*^-'*j f 



FIG. 13. Pneumococcus, showing capsule, from pleuritic fluid of infected rabbit, 

 stained by second method of Hiss. (Williams.) 



in that the colonies on blood-serum are viscid and like irregular flecks of mucus. 

 The characteristic culture is a glucose agar stab. (Reaction must not exceed +0.5.) 

 From the line of puncture there are flail-like projections extending outward from 

 one-fifth to one-fourth of an inch. The capsule persists on ordinary culture media. 

 This organism resembles the Streptococcus of Bonome of the French. 



In a study of blood and sputum cultures from thirty- two cases of lobar 

 pneumonia Hastings and Boehm found blood and sputum positive bacteriologically 

 in eleven cases. In nine of these cases the pneumococcus was isolated and in 

 two a haemolysing streptococcus. In the other twenty-one cases the sputum 

 cultures were bacteriologically positive in eighteen of the cases and negative in 

 three. In nine cases the pneumococcus was isolated, in two cases B. coli, in 

 one case M. catarrhalis, in one case a staphylococcus, in two cases staphylococci 

 and streptococci, in one case B. influenzas. The percentage of positive blood 



