106 LOCALIZED INFECTIONS OF PUS NATURE 



alive and capable of producing disease for several 

 months if protected from light. If the sputum be 

 dried and powdered, so that it could be inhaled, the 

 cocci live for a few days in diffused light. Direct 

 sunlight kills them almost immediately. They are 

 killed at 52 C. or 126 F. in ten minutes. It is said 

 that the best way to disinfect sputum is by the addition 

 of about one-third alcohol. The pneumococcus itself 

 has a very low resistance to any of the ordinary 

 disinfectants, being killed in a few minutes. 



Most of the lower animals, particularly mice and 

 rabbits, but not birds, are susceptible to the pneumo- 

 coccus. However, a true pneumonia as seen in man has 

 not been produced artificially. The pneumococcus 

 produces a small quantity of poison aside from itself, 

 but acts chiefly by reason of substances within the 

 germ cell. It has been found that there are four closely 

 related varieties of pneumococci capable of causing 

 pneumonia and that against two of them it is possible 

 to produce in horses a powerful antiserum. In a given 

 case of pneumonia the causative strain of cocci is 

 isolated and studied ; if it belong to one of the two proper 

 varieties the respective antiserum may be injected 

 under the skin or into a vein. The death-rate of pneu- 

 monia for these two kinds has been somewhat reduced 

 by this treatment. The use of vaccines has not been 

 followed by uniformly favorable results. The blood 

 in pneumonia contains some agglutinins, but they are 

 not of much value in diagnosis 



