DISCUSSION 137 



tion. For example, it has been known for many years that for the pro- 

 duction of delayed allergy to bacteria it is mandatory that the intra- 

 dermal, subcutaneous or intraperitoneal route be used. It is of special 

 interest that the intravenous injection of bacterial cells results in the 

 development of an immune state (serum antibody formation) but does 

 not result in the induction of delayed allergy. This result in relation to 

 delayed allergy would seem generally applicable, since it has been shown 

 to hold true for the tubercle bacillus, the streptococcus and the pneu- 

 mococcus. Moreover, in tuberculous patients with delayed allergy to 

 tuberculin, it has been repeatedly observed that invasion of the blood 

 stream by tubercle bacilli results in the reversion of the previously 

 positive tubercuhn reaction to a negative one. These data obtained in 

 relation to delayed bacterial allergy may be interpreted in at least two 

 ways : either the intravenous route bypasses the cell or cells of the 

 reticuloendothelial system concerned with the production of delayed 

 sensitivity, intradermal and subcutaneous deposits of antigen having an 

 obligatory voyage through lymphatics and cells of the lymph nodes; 

 or, on the basis of the abohtion of delayed allergy in the presence of a 

 specific bacteraemia, the possibility for simultaneous sensitization and 

 desensitization exists, the latter usually in the ascendency when antigen 

 gains access to the circulation. 



