IMMUNOLOGICAL RELATIONSHIPS 335 



Spiroclield pallida dialyzed materials with heterolooous filtrates 

 {B. typliosus) . P. Boqiiet (1935) obtained cross reactions with fil- 

 trates of B. Icpiscpticus and B. coU, and Alechinsky with B. coli 

 and Staphylococcus filtrates. 



From the abo\e cited experiments, it becomes obvious that 

 cross reactions may be obtained Avith totally tnirelated microor- 

 ganisms. The observations of Ecker and Welch (1930), and 

 Stolyh^vo may suggest a broad specificity inasmnch as it seemed 

 to these authors that stronger reactions may be obtained ^vith 

 homologous filtrates. The question, however, can only be defi- 

 nitely decided in observations with materials closely titrated to 

 the end-point as illustrated by the following experiment: 



B. typ}iosu.s and meningococcus "agar washings" filtrates were 

 titrated for skin-preparatory potency against constant intravenous 

 doses (Method II) and for reacting potency against constant 

 skin-preparatory doses (Method III) . It has been a consistent 

 observation that the meningococcus filtrates possess, as a ride, 

 two to three times higher reacting potency than B. typlwsus "agar 

 washings" filtrates, and vice versa, the B. typhosus filtrates pos- 

 sess at least fi\e times higher skin-preparatory potency than the 

 meningococcus "agar Avashings" filtrates. This observation was 

 considered as advantageous in order to determine the question 

 of the specificity of the phenomenon. For this pinpose various 

 diliUions of meningococcus and B. typlwsus "agar washings" 

 Idtrates were used for a single preparatory injection. A group of 

 three rabbits Avas used for each dilution. All the rabbits received 

 25 meningococcus reacting imits. In this manner, it was foiuid 

 that 0.25 c.c. of meningococcus "agar ^vashings ' filtrates diliUed 

 1:200, and 0.25 c.c. of B. typhosus "agar ^vashings" filtrates di- 

 liUed 1:1000 Avere the highest dilutions capable of eliciting the 

 state of reactivity. It could be concluded then, that provided a 

 highly reactive material Avas used for the intravenous injection, 

 the skin-preparatory potency of the heterologous filtrate ranged 

 higher than that of a homologous filtrate. 



Furthermore, in a series of investigations recorded in Chapter 

 IX, it was clearly demonstrated that whilst the state of reactivity 

 is elicited exclusively by certain bacterial principles, potent react- 

 ing factors may be obtained from non-bacterial preparations, i.e., 

 combinations of animal proteins ^vith homologous antisera and 

 agar (possibly with a lesser regularity) . 



These experiments seem to bring incontrovertible proof as to 



