ANTIGENICITY OF PNEUMOCOCCUS 343 



elaboration of antibacterial substances, the intravenous method is 

 the one of choice. 



INTRADERMAL INJECTION 



The intradermal injection of pneumococci and their products 

 may be followed by the development of the immune state. Goodner 

 (1928), 525 " 6 in studying the pathogenic action of living pneumo- 

 cocci inoculated into the skin of rabbits, observed that the serum 

 of animals surviving infection had acquired protective antibodies. 

 Furthermore, within five days after a single intradermal injection 

 of dead pneumococci, the normal rabbit developed resistance to in- 

 fection. In two communications appearing in 1930, Julianelle 687 " 8 

 reported that repeated injections of small doses of suspensions of 

 heat-killed pneumococci of Types I and III into the skin of rab- 

 bits induced species-specific but in no case type-specific antibodies 

 for the organisms. However, animals developing only species-spe- 

 cific antibodies after intradermal vaccination still possessed the 

 ability to form type-specific immune substances when subsequently 

 given intravenous injections of pneumococci of fixed types. De- 

 spite the failure of heat-killed pneumococci when injected intra - 

 dermally to evoke the formation of type-specific antibodies in the 

 rabbit, devitalized cultures do, nevertheless, render the animal ac- 

 tively immune to infection with pneumococci not only of homolo- 

 gous but also of heterologous type. The injection into the skin of 

 soluble derivatives of Pneumococcus in Julianelle's experiments 

 was not followed by the production of active immunity. The de- 

 struction or inactivation in the skin of rabbits of type-specific 

 antigen injected intradermally was later observed by Harley 

 (1935). 593 The somatic protein, on the contrary, appeared to be 

 unaffected and stimulated the formation of species-specific anti- 

 bodies. 



The observation of Julianelle was significant in that it revealed 

 a hitherto unknown property of the epidermal cells of the rabbit. 



