460 BIOLOGY OF PNEUMOCOCCUS 



tion of homologous capsular polysaccharide. The reaction tended 

 to be larger in area but not so sharply defined as that in the ac- 

 tively immune rabbit. A peculiar phenomenon observed was the 

 disappearance and subsequent recurrence of the reaction in some 

 instances without intervening intradermal injections.* The long- 

 est period of time over which spontaneously recurring reactions 

 were observed was slightly more than six months. The injection of 

 pneumococcal protein into immune horses, and of type-specific 

 polysaccharide or protein into normal horses or into horses im- 

 munized with heterologous types of pneumococci, resulted in no 

 reaction. The experiments, though incomplete, point to a local 

 reaction in the dermal tissues between antigen and circulating 

 antibody or to a fixation of antigen by antibody in the dermal 

 cells rather than to a hypersensitive state of the cutaneous tissues. 

 Francis and Tillett (1931) 479 succeeded in demonstrating skin 

 reactions to capsular polysaccharides of pneumococci of Types I, 

 I, and III in rabbits actively or, under certain conditions, pas- 

 sively immunized to organisms of one or another of these types. 

 The reaction resembled that of Arthus, and was demonstrable only 

 when type-specific precipitins for the homologous polysaccharide 

 were present in the blood of the rabbit. A reaction was elicited in 

 84 per cent of actively immunized animals, the serum of which 

 contained type-specific precipitins, and a positive result was ob- 

 tained in all rabbits passively immunized with antipneumococcic 

 horse serum. Attempts to transfer the reactive principle from im- 

 mune rabbit to normal rabbit were unsuccessful. The recipients 

 in the latter group possessed no demonstrable circulating type- 

 specific precipitins. Francis and Tillett concluded that the reac- 

 tion produced by specific capsular carbohydrates is always asso- 

 ciated with a well-grounded type-specific immunity. 



SKIN REACTIONS IN LOBAR PNEUMONIA 



The value of skin reactions to tuberculin and to diphtheria 

 * Compare with observation of Julianelle, page 456, ante. 



