732 ANTIGENIC PROPERTIES OF THE BACTERIAL CELL 



used to elicit allergic reactions in sensitive animals. We believe that these facts are 

 essential to the understanding of bacterial allergic reactions of all types. 



We are entirely in the dark regarding the property which lends to a chemical com- 

 plex the power of arousing antibody formation. It is lost in the isolated soluble specif- 

 ic or residue substance and is retained by the protein. It is lost in protein by racemi- 

 zation, is altered by various forms of denaturation, and remains inherent in the pro- 

 tein in spite of modifications of the specificity of the molecule by the introduction, 

 usually into the aromatic amino acids, of methyl and other radicles. We know nothing 

 specific about this property except that it is possessed only by nitrogenous sub- 

 stances, proteins, or protein-like molecules of large size, all of them non-diffusible 

 and colloidal. It appears, therefore, that in order to be capable of antibody production 

 a certain chemical structure, together with non-diffusibility, is indispensable; and 

 since lack of experimental approach occasionally justifies speculation, we may suggest 

 that, teleologically considered, antibody formation represents an emergency mecha- 

 nism by means of which the body can deal with nitrogenous foreign substances that 

 cannot be taken care of either by intracellular digestion in the fixed-tissue cells or by 

 simple disposal by the excretory organs. Just how the antibodies assist in increasing 

 the ability of the body to get rid of foreign antigenic substances has not been followed 

 in detail, but we do know that in bacterial disease antibodies make possible in some 

 cases lysis, in all cases phagocytosis, and that in such conditions as serum sickness, 

 where an easily determined antigen is in an unformed state, the antigen disappears 

 from the blood stream in an inverse ratio to the appearance of antibodies. 



