PROTECTION AGAINST RUNTING 325 



The third series (88 animals) received nothing or physiological 

 saline and were followed as normal controls. The observed 

 results concerned runting syndrome and acquired tolerance to 

 CBA skin grafts. 



Concerning runtiug: between day o and day 35, 41 per cent of 

 series i animals died of runting, 63 per cent in series 2 and o per 

 cent in series 3 ; with powerful antisera the difference was still more 

 striking (23*5 per cent death in series i versus 64 per cent in 

 series 2). The weight curves of survivors of series i and 2 were 

 almost superimposable and much below the weight curve of 

 series 3. 



Concerning tolerance: animals of series i exhibited a significant 

 quantitative and qualitative increase in tolerance of CBA skin 

 grafts. The immunological specificity of the antisera used 

 was ascertained by specific haemagglutiuation and specific 

 immuno toxicity. 



Acknowledgements 



We are very indebted to Dr. Francine Toullet, who helped us throughout 

 this work mainly in performing haemagglutination tests. We are grateful to 

 Miss F. Kelly who helped us in the statistical analysis. 



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