§2] 



ACCLIMATIZATION TO CHEMICAL AGENTS 



29 



rattlesnake poison (Crotalophorus tergeminiis). While no 

 unacclimatized pigeon could resist 1 drop of a 6.8% solution of 

 venom in glycerine, pigeons inoculated with at first weak, then 

 gradually increasing solutions, came at last (after 178 days) to 

 resist 4 drops of the glycerine venom mixture. Likewise Kan- 

 THACK ('92) succeeded in acclimatizing two rabbits and a hen 

 to serpent's venom. 



Very similar are the experiments of Ehelich ('91). This 

 investigator fed white mice (which are killed by ^\ of their 

 weight of a 0.0005% solution of ricin, hypodermically in- 

 jected) upon food cakes soaked in a weak solution of the poison. 

 After feeding them for a varying length of time upon constantly 

 increasing solutions, he determined the maximum solution 

 which, hypodermically injected, they would withstand. If we 

 call the maximum solution which the unacclimatized organism 

 will withstand our unit of immunity, we can express the degree 

 of immunity of the acclimatized organisms by the strength of 

 solution (expressed in terms of that unit) which they can resist. 



The following table, taken from Ehelich's paper, shows 

 the gradual increase of immunity as a result of feeding on the 

 poison : — 



TABLE IV 



Thus after the first 4 or 5 days the immunity rapidly in- 

 creased ; so that, while the solution of 0-77-7/01517 kills normal 



