THE PNEUMOCOCCUS 65 



is slightly grayish by reflected light. It produces considerable acid, thus acidify- 

 ing and usually coagulating litmus milk. It produces acid inynulin media which 

 the Streptococcus fails to do. The colony is smaller and more transparent than a 

 Streptococcus colony. In sputum or other pathological material it is best recognized 

 by the presence of a capsule inclosed in which are two lance-shaped cocci with their 

 bases apposed. In artificial culture we rarely get the capsule. It also sometimes 

 grows in short chains like a Streptococcus. The best medium for differentiating is 

 the serum of a young rabbit; in this it grows as a diplococcus, while streptococci 

 show chains. Kosenow has by combining passage in animals with culturing sym- 

 biotically with B. subtilis changed the Pneumococcus into a haemolytic Streptococcus. 

 The best method of isolating it in pure culture is to inject the sputum into the 

 marginal ear vein of a rabbit or subcutaneously into a mouse. Death results from 

 septicaemia in about two days and the blood teems with pneumococci. Usually 

 the Pneumococcus quickly loses its virulence, and 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 maintains 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 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. 

 Results from the use of antipneumococcic sera have been of only slight value. Such 

 sjira^are useless against infections with_other strains. Vaccines appear to be value- >1 - 

 less in pneumonia but may be useful in local infections. They probably stimulate 

 opsonin production. Oscar Richardson has reported an organism in cases of 

 lobar pneumonia, cerebrospinal meningitis, mastoid disease, etc., bearing resemb- 

 lance to both pneumococci and streptococci the Streptococcus capsulatus. Other 

 names are Streptococcus mucosus and Pneumococcus mucosus. It is very virulent 

 for mice but less so for rabbits. Park isolated it twice from 20 cases of pneu- 

 monia. It differs from the Pneumococcus 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 ^ to 24 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 32 cases of lobar pneu* 

 monia Hastings and Boehm found blood and sputum positive bacteriologically 

 in ii cases. In nine of these cases the Pneumococcus was isolated and in 2 

 a haemolysing Streptococcus. In the other 21 cases the sputum cultures 

 were bacteriologically positive in 18 of the cases and negative in 3. In 

 9 cases the Pneumococcus was isolated, in 2 cases B. coli, in i case M. catar- 

 rhalis, in i case a Staphylococcus, in 2 cases staphylococci and streptococci, 

 in i case B. influenza. The percentage of positive blood cultures was 30.3. 

 Cole obtained 30% of positive blood cultures. The blood was taken into flasks of 

 bouillon in dilution of 1-50. 

 5 



