30 CHEMICAL AGENTS AND PROTOPLASM [Cn. I 



mice, those acclimatized during 21 days resist -j-gVo to - 

 occasionally 3"-^, corresponding to a grade of immunity of 200 

 to 800. 



By fundamentally similar procedures CALMETTE ('94) has 

 rendered rabbits immune to the action of strong doses of the 

 venom of Naja tripudians (cobra) and of Pelias berus. 



Still more recently MARMIER ('95) has isolated a toxin 

 produced by anthrax bacteria reared in a peptone-glycerine 

 solution. Inoculated into an animal sensitive to anthrax, 

 this toxin produces, in certain doses, death by cachexy. By 

 employing suitably graduated doses, however, one can obtain 

 immunity of the organism to anthrax, as one does to the venom 

 of serpents. 



Some attempts to produce acclimatization in lower organisms 

 have been made by Dr. H. V. NEAL and myself. Stentor was 

 employed as the object of experimentation. We reared two 

 lots of Stentors under similar conditions except that Lot 1 was 

 cultivated in water and Lot 2 in 0.00005% HgCl 2 . After the 

 lapse of two days both were put into a killing solution of 

 0.001% HgCl 2 , and the second lot was found to survive longer 

 than the first. The mean resistance period to the killing solu- 

 tion of the lot reared in water was 83 seconds; of that reared 

 in 0.00005% corrosive sublimate, 304 seconds. Similar results 

 were obtained in other experiments. In Fig. 1 a curve is 

 given showing the relation between strength of culture solu- 

 tion and period of resistance. From this curve, based upon 

 132 determinations, it appears that the resistance period varies 

 directly with the strength of the solution in which the protoplasm 

 has been cultivated. 



This law holds good, however, only within certain limits. 

 If the culture solution is too strong, above 0.0001%, the 

 organism will be weakened by it so that it cannot resist the 

 killing solution so long as those reared in water can. 



A similar effect of heightened resistance to quinine is ob- 

 tained by cultivating organisms in quinine. 



Experiment shows that a slight increase of the resistance 

 period follows subjection to the culture for one hour only; and 

 that the degree of acclimatization varies directly as the time 

 of subjection. 



