UNSOLVED PROBLEMS 619 



vein of the same animal evokes the formation of antibodies of strict 

 type-specificity homologous with the type of antigen employed. If 

 the nature of the tissue reaction in each case could be discovered, 

 our conception of immunological processes would acquire further 

 definition. 



The local fixation of bacteria at the site of injection into the 

 skin of rabbits may allow opportunity for the action of tissue en- 

 zymes to inactivate or dissociate capsular antigen of the bacterial 

 cell, leading to or accounting for the diminution or loss of type- 

 specific response. The assumption is susceptible of proof. 



ANTIBODIES AND ANIMAL SPECIES 



The immunological differences between antipneumococcic serum 

 produced in rabbits and that produced in horses have been men- 

 tioned in earlier parts of the text. There may be, of course, quan- 

 titative differences in the antibody content of the two serums ; the 

 antibody may exist in one fraction of one and in another fraction 

 of the other serum, and its affinity for antigen may be modified by 

 its particular conjugation with some serum component. We are 

 now learning that the molecular size of the antibody or the physi- 

 cal state in which antibody exists in immune serum may account 

 for these differences in serological behavior. 



SKIN REACTIONS 



The history of the phenomena to be observed following the in- 

 tradermal injection of pneumococcal materials is incomplete and 

 confused. The diversity of antigenic preparations employed, and 

 the variety of inflammatory reactions induced in the cutaneous tis- 

 sues and classed as positive, largely account for the confusion. 

 The antigens comprising somatic protein and carbohydrate and 

 capsular polysaccharide should be prepared in accordance with 

 the most advanced technique and should be selected as representa- 

 tive of the chemical and immunological individuality interpreted 

 in terms of the specific reactions of the organisms as a whole. The 



