ACTION OF ALKALIES ON PLANARIA. 339 



endured through the period of the experiments. A further test 

 by the susceptibility method was suggested. If any acclimation 

 occurred, worms that had been kept in a non-injurious concentra- 

 tion of alkali should be less susceptible to a lethal concentration of 

 alkali than control worms. Stocks of worms were kept in water 

 made alkaline to pH 8.8 and 9.0, respectively, with NaOH, and 

 were compared as to susceptibility to a higher concentration of 

 NaOH with control worms living in ordinary water, pH S.c. 

 Tests were' made every third day over a period of ten days. No 

 difference in susceptibility between experimental and control 

 worms was found. The resistance of Planaria to alkali was, 

 therefore, not increased by continuous exposure, up to ten days, 

 to alkaline water. 



DISCUSSION. 



The experiments reported in this paper show that in general 

 the rate of oxygen consumption is accelerated in water made more 

 alkaline than normal, within physiological limits, by sodium or 

 ammonium hydroxide. This increase in the respiratory rate lasts 

 as long as the worms remain in the alkaline water, at least up to 

 two weeks. Upon return to water of normal alkalinity, the re- 

 spiratory rate drops at once. No evidence of any acclimation to 

 the alkaline environment appeared in the course of the experi- 

 ments. The oxygen consumption remained at a supernormal 

 figure during continued exposure to the increased alkalinity. Sus- 

 ceptibility tests also showed no increased tolerance to alkali as a 

 result of living for some time in water of increased alkalinity. 



The question of the cause of the accelerated respiratory rate in 

 alkaline water is of interest but the present experiments throw no 

 light on the matter. It is rather generally accepted that alkalies 

 increase permeability or have some other surface action (e.g., 

 Osterhaut, '14, and Warburg, '10). Such surface changes might 

 well be the cause of the acceleration of the respiratory rate. It 

 is not probable that penetration of the alkali into the interior is a 

 factor in the acceleration for although ammonia penetrates cells 

 readily it is believed that sodium hydroxide does not penetrate 

 until the surface is actually injured. Since both alkalies caused 

 an increase in the rate of oxygen consumption, the effect appears 

 to be a surface one. 



