588 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Protozoa. 



Adaptation and Immunity of Infusorians to Ethyl-alcohol.* — 

 J. Frank Daniel has studied the acclimatization of Infusorians to ethyl- 

 alcohol, and the effects of this acclimatization on their resistance to 

 other chemicals. His chief conclusions are thus summarized : — 



In certain strains of Stentor cceruleus, and in Spirostomum ambiguum, 

 it was found that living for a few days in 1 p.c. ethyl-alcohol increases 

 the resistance of the animals to a stronger solution of the same sub- 

 stance — ethyl-alcohol. This increased resistance is shown (1) in the 

 fact that the organisms are not so quickly killed in a lethal solution ; 

 (2) in the fact that they may continue to live in a stronger solution — 

 stronger than that in which they could live before acclimatization. 

 Different species of Infusoria and different strains of the same species, 

 living under dissimilar environmental conditions, showed various degrees 

 of normal resistance to alcohol, and very different capacities for becoming 

 acclimatized to it. 



In Stentor cmruleus one strain, designated as E, manifested a high 

 normal resistance, but this resistance was increased little or not at all 

 by remaining in 1 p.c. alcohol ; while another strain F, had a low 

 normal resistance, which was readily increased by living in a weak 

 acclimatizing medium. 



Incidentally, similar differences in the resistance of different sorts 

 of Infusoria to other chemicals were observed. Thus, Spirostomum 

 withstood about eight times as concentrated a solution of hydrochloric 

 acid as did Stentor. Marked differences are likewise observable among 

 individuals of the same culture when tested for resistance to different 

 chemicals. 



Acclimatization to alcohol is shown not alone in an increase of resist- 

 ance to a stronger solution, but in changes in the behaviour of the 

 organisms. The unacclimatized animal responds to the stronger chemical 

 by powerful motor reactions, while the acclimatized organism shows much 

 slighter activity. In a weak solution of alcohol (1 p.c.) the beginning 

 of acclimatization is usually evident within a few hours. This increases 

 in a fairly uniform ratio until about the fourth day, at which time a 

 maximum degree of immunity may be expected. The degree of resist- 

 ance produced corresponds in a measure to the strength of the alcohol 

 used as an acclimatizing medium. As compared with the resistance 

 produced by a 1 p.c. medium, that due to ^ p.c. is lower in degree. In 

 a medium much stronger than 1 p.c. the correspondence does not hold, 

 since stronger solutions decrease the resistance by producing injury to 

 the organism. 



The fact that in these experiments some strains show little or no 

 capacity for becoming acclimatized to alcohol although tried for long 

 periods of time and with refined methods, makes it questionable whether 

 acclimatization takes place so readily and to so high a degree as is 

 commonly supposed. Tolerance, or acclimatization, to ethyl-alcohol 

 does not increase the resistance of the organisms to other chemicals. 

 On the contrary, it usually renders the animals less resistant to other 

 agents. This matter was studied in detail in Stentor and Spirostomum 



* Journ. Exper. Zool., vi. (1909) pp. 571-611. 



