PNEUMOCOCCAL VACCINES 503 



disturbances of nutritional function, by intercurrent or chronic 

 disease, or by undue physical strain, to whom pneumonia may pre- 

 sent an especially serious hazard, and in the case of large bodies of 

 men assembled from many sections of the country and living for a 

 time under crowded conditions, the protection, such as it is, af- 

 forded by the parenteral administration of suitable pneumococcal 

 materials should not be disregarded. To be sure, the biological 

 agent should be prepared with proper attention to the type or 

 types of Pneumococcus prevalent at the time, the kind of vaccine 

 selected should represent the best immunological practice, and the 

 injections should be repeated at frequent intervals. The danger of 

 pneumonia to man both individually and in masses merits the ap- 

 plication of such preventive measures as we possess, imperfect as 

 they are, until an antigen more closely approaching the ideal is 

 devised. 



VACCINE TREATMENT OF PNEUMONIA 



The possible curative action of bacterial vaccines in pneumo- 

 coccal infections more properly belongs to a discussion of the 

 clinical features of the disease. The reader in search of this infor- 

 mation is referred to the volume by Heffron, 601 where a more ex- 

 haustive treatment of the subject will be found. However, in order 

 to round out the description of the many biological activities of 

 Pneumococcus, there are included in the present chapter refer- 

 ences to the effect of specific vaccines administered during the 

 course of pneumococcal disease, but only a few of the many obser- 

 vations will be noted. The rationale of vaccine therapy in pneu- 

 monia is based on the unusually rapid development of type-specific 

 antibodies created by the parenteral injection of suitable anti- 

 genic agents. The introduction of pneumococcal antigens into a 

 body already infected with millions of pneumococci and therefore 

 having its tissues permeated by the antigenic constituents of the 

 bacteria in their native condition would, because of certain theo- 

 retical considerations, seem paradoxical. There is the possibility, 



