IMMUNOLOGICAL BEHAVIOR 107 



and coli rough; Typhoid rough strains and Sera R-30'^ and 

 Horses 5/ 15 15/ ). Moreover, the 2 B. typhosus rough 



,125, ! lie,. / Uh' - ■' _ ^ 



variants (Ty Tl 238 ser.o and Ty Tl 245 ser.2) , both derived 

 from tlie same stock strain (Ty Tl) , and a third B. typhosus 

 rough xariant (Ty 870 phages) deri\ed from another stock strain 

 (Ty 870) varied in the degree of their neutraHzabihty l)y anti- 

 rough sera (Horsesy^^^ and ^/nd ■ The question as to whether 

 the "rotigh" reacting factors are able to stimuLate antibodies 

 against normal reacting factors is left open.^ 



In the Avork which follo^vs, an attempt Avas made to correlate 

 the above findings with the morphological appearance of colonies, 

 agglutinability and virulence of the various strains and also ^vith 

 the serum precipitability of the filtrates studied. 



Morphological appearance of colonies and the neutralizability 

 of reacting factors: 



As is seen from above, the stock strains of B. typhosus produced 

 reacting factors of various degrees of neutralizability. The Ty Tl 

 stock strain, producing factors of high neutralizability and anti- 

 genicity and apparently the simplest in antigenic structure, was 

 morphologically rough-smooth and ^vas capable of prompt trans- 

 formation into complete roughness. The reacting factors of the 

 remaining stock strains which differed in neutralizability and 

 Avere considered more complex did not display any difference in 

 the colony morphology, all appearing normal. Neither ^vere these 

 strains transformed into rough variants in spite of persistent at- 

 tempts. It appears, therefore, that strains of normal colony ap- 

 pearance differ in the neutralizability of reacting factors ^vhich 

 they produce. 



The different rough variants produced by passage through 

 immune serum and bacteriophage appeared of morphologically 

 identical colony structtne, ^vhilst they differed in the neutraliza- 

 bility of their reacting factors. 



The passage of stock strains through mice ^vhich may or may 

 not result in a change of neutralizability ^vas not accompanied 

 by any changes in the morphology of the colonies. 



'^The objection to this work which may be raised is that tlic toxoid formation 

 (described later) may account for the resuUs. This is obviously not the case since 

 neutralization of the reacting factors of the variants ^\as obtained wiili homologous 

 sera where the stock sera failed to do so. 



