132 LOCAL ILSSIIE REACTIVITY 



scss a lower susceptibility to the plK-nomcnon than domestic 

 rabbits. 



Apit/ (k)-}-^^') noted a lower dei>iee ot reacti\ity in the winter 

 than during the smnniei months. 



Gratia and Linz (19326) lomid that yoimg ral)l)its one to two 

 months old reacted more se\erely than old ones. In contrast to 

 this, howe\cr, the new-born aj^jjeared refractory to the phenome- 

 non. Thus, one rabbit ga\e birth to seven young ones; at the day 

 ot birth the skin of one of the rabbits was prepared with 0.2 c.c. 

 of an active B. coli filtrate. Twenty-four hours later 0.25 c.c. of 

 the fdtrate was injected intraperitoneally. No reactions w^ere ob- 

 tained. Another new-born animal ^vas treated the same Avay on 

 the second day of its life Avith a negative result. Tw^o more rabbits 

 were injected on the seventh day, two more on the fifteenth day, 

 all of the rabl)its showing negative residts. The last new-l3orn 

 rabbit ^vas tested on the twenty-first day. This time the reaction 

 was strongly positive. Llyeda (1934) also claimed that yoimg 

 rabbits are less susceptible to the jjhenomenon of local skin reac- 

 tivity to vibrio cliolerae than adidt rabbits. 



Witebsky and Neter (1936) studied extensively the question of 

 age susceptibility. Highly potent B. iypJiosus and meningococcus 

 filtrates were used by these authors. One-tenth to 0.2 c.c. of the 

 respective filtrates were injected. 



Out of 16 litters of 78 yoimg ral)bits, one and a half to five 

 weeks old, 12 litters of 58 animals did not display any reaction. 

 The remaining 20 yoinig ral)bits belonged to 4 litteis only. Two 

 of these litters (three to five weeks old, resj^ectively) of 9 animals 

 were strongly positive. The other 2 litters (two weeks and fom 

 to five weeks old, respectively) consisted of 1 1 animals; 3 of them 

 were negative, one sho^ved a doubtfid reaction and 7 Avere posi- 

 tive. Thus, a high percentage of yoimg rabbits ^vere refractory to 

 the phenomenon. 



The phenomenon-negative litters were again tested for periods 

 of one to two weeks with the same or heterologous filtrates. The 

 same amount of filtrate \vas used as in the first experiment irre- 

 spective of the increased weight of the young rabbits. Many, but 

 not all, of the originally negative animals were positive at the 

 second, sometimes only at the third or fourth repetition of the 

 test. It appeared beyond doubt from these experiments that there 

 existed a definite correlation l^etween the aging of rabbits and 

 their ability to react to the phenomenon. 



