502 BIOLOGY OF PNEUMOCOCCUS 



to human beings and the antibody response measured by testing 

 the protective strength of the serum of the subjects so treated. 

 The results of the investigation proved that immunity against 

 pneumococci may be produced in man by the injection of soluble 

 products prepared from the microorganisms. Among the pneumo- 

 coccal materials employed was a water-soluble substance that 

 failed to give biuret and Molisch reactions,* lacked the property of 

 precipitating immune serum, and yet immunized white mice. The 

 substance was considered by the authors to differ from any hith- 

 erto studied fraction of Pneumococcus. All the preparations tested 

 for antigenicity, as well as dried organisms, evoked an increase in 

 protective antibodies in the serum of the individuals treated. The 

 degree of immunity established from a single injection of a two- 

 milligram dose of antigenic substance, as measured by protective 

 antibodies in the serum, compared favorably with that found in 

 the serum of convalescent pneumonia patients. The duration of the 

 immunity following the use of vaccine or of the fractions employed 

 varied in different individuals, but in some cases persisted for at 

 least a period of three months. 



Wadsworth, 1465 in a discussion of the practical limitations of 

 the vaccinal prevention of pneumococcal infection, differing with 

 the opinion of Lister, Ordman, and others, stated that with rare 

 exceptions pneumonia does not yield to any form of prevention 

 and that the protective inoculation with pneumococcal vaccine ad- 

 vocated by some authorities as a public health measure is not prac- 

 tical. Granting the soundness of the latter portion of the state- 

 ment, prevention, nevertheless, as a measure for sparing the indi- 

 vidual from an attack of pneumonia is not to be dismissed so 

 lightly. The very definite limitations of this method of prophy- 

 laxis, such as the heterogeneity of serological types and the brief 

 spell of immunity following vaccination are freely admitted. How- 

 ever, in the case of individuals debilitated by age, by the effects of 



* In another part of the same paper the authors stated that the substance 

 might contain a polysaccharide as a part of its constituency. 



