PNEUMOCOCCIC VACCINE 489 



ture, but no other symptom. Macfadyen l obtained an 

 endotoxin by triturating cultures with liquid air. 



Immunity and anti-serum. Immunity can be conferred 

 on susceptible animals by treating them with minute 

 doses of virulent cultures, or with attenuated cultures. 



Blake and Cecil found that an animal which survived 

 a minute subcutaneous dose of virulent culture was 

 subsequently immune to an intratracheal inoculation of 

 100,000, the minimal infecting dose for an untreated 

 animal. Animals which had recovered from an attack of 

 experimental pneumonia were refractory to intratracheal 

 inoculation of the same culture. An attack of Type I 

 pneumococcal pneumonia was found to confer little 

 protection against Type II pneumococcal pneumonia. 



An anti-serum may be prepared by inoculation with 

 increasing doses, first of killed cultures of the virulent 

 organism followed by doses of the living organism. This 

 anti-serum is protective experimentally and has been 

 used in the treatment of pneumonia and other pneumo- 

 coccic infections, but the results have not been very 

 encouraging, partly, perhaps, because the homologous 

 type serum has not been used. 



Vaccine. A vaccine has been found of service in the 

 treatment of chronic pneumococcic infections, in catarrhal 

 conditions in which the pneumococcus is one of the 

 associated organisms, and has also been employed in 

 acute croupous pneumonia ; the doses range from 20 to 

 50 millions. In all these cases the vaccine should be 

 an autogenous one. Wright (loc. cit.) advised a vaccine 

 for prophylactic inoculation against pneumonia on the 

 Rand, and Lister (loc. cit.) recommends for this purpose 

 three inoculations at weekly intervals, each dose con- 

 sisting of 6,000 million cocci of each group against which 

 immunity is desired. 



1 Brit. Med. Journ., 1906, vol. ii, p. 776 (Refs.). 



