486 BIOLOGY OF PNEUMOCOCCUS 



found that the highest degree of protection followed in the case of 

 Type I vaccine, less was afforded by suspensions of Type II cocci, 

 while Type III preparations induced the least protection. In test- 

 ing polyvalent vaccines, Bengston observed that their use re- 

 sulted in more definite protection against pneumococci of Types II 

 and III than was noted after the use of monovalent vaccines, sug- 

 gesting the production of a certain amount of cross-protection. 

 The tests, as a whole, showed that commercial polyvalent pneumo- 

 coccal vaccines afforded protection in mice against amounts of 

 virulent cultures ranging from zero to one million fatal doses in 

 the case of Type I organisms, from zero to ten thousand fatal 

 doses in the case of Type II, and only from zero to one hundred 

 fatal doses of Type III cultures. 



Before employing vaccines or other immunizing agents made 

 from pneumococci, the preparations, as is the case with other bio- 

 logical products, should be subjected to some suitable test or tests 

 to determine their antigenic strength. While it is obvious that ef- 

 fects in animals cannot be accurately translated into effects on 

 man, yet determinations on laboratory animals furnish informa- 

 tion concerning the probable immunizing action of bacterial agents 

 or derivatives in the human body. 



ROUTE AND SPACING OF INJECTIONS 



Animal experimentation has demonstrated that the intravenous 

 introduction of pneumococcal antigens, as compared to other 

 methods, stimulates a more rapid and energetic immunizing re- 

 sponse. The technique, despite certain and largely avoidable haz- 

 ards, is applicable to man. As a matter of convenience, however, 

 the subcutaneous route, especially in the prophylactic treatment 

 of large numbers of individuals, is to be preferred. The intrader- 

 mal injection of pneumococci, as shown experimentally in rabbits 

 by Goodner, 525 " 6 ' 529 and of soluble specific substance, as demon- 

 strated in man, by Francis, 474 Francis and Tillett, 478 and by Fin- 

 land and Sutliff, 446 " 7 calls forth the prompt appearance of specific 



