482 MINNA E. JEWELL 



there may be a greatly increased oxygen metabolism, which is, 

 however, a destructive metabolism accompanied by cessation 

 of growth or even by regressive changes leading to death. Since 

 in basic media the increased CO2 production is accompanied by 

 a pathological condition resulting in death, we must regard this 

 high oxygen metabolism also as a destructive metabolism. From 

 this we see the fallacy of using oxygen metabolism as a criterion 

 of what is favorable for general metabolism in judging the suita- 

 bility of a water for animals. Development, growth, or possibly 

 regeneration must rather be relied upon. 



It will be noted that in both of the above experiments the 

 regeneration of the tadpoles in 10 cc. of the base was better than 

 that of the controls. It was, however, observed during the 

 experiment that although the initial hydrogen ion concentration 

 of these solutions was decidedly on the basic side of neutrality 

 (pH about 9), that by the time the solution was changed it 

 was slightly acid (pH about 6.8). For this reason another 

 series of experiments was planned, using the same concentra- 

 tions, but a larger volume in proportion to the size of the 

 tadpoles, and changing it oftener. Two parallel series were run, 

 each consisting of five small tadpoles in 1 liter of distilled water, 

 0.00025N NaOH and 0.0005N NaOH (25 and 50 cc. O.OIN 

 per liter). The experiments were carried out in 2-quart mason 

 jars kept tightly sealed, and containing test-tubes of Ba(0H)2 

 solution to absorb the CO2 from the air above the water. The 

 results of this experiment are given in table 4. Due to the CO2 

 produced by the tadpoles, the distilled water became slightly 

 acid and the NaOH solution less basic ; however, it was no longer 

 neutralized. The retardation to regeneration is very marked 

 in 25 cc. per liter, while 50 cc. proved fatal in two days. 



These results show that the reason corresponding solutions 

 (5 and 10 cc. O.OIN base in 200 cc.) produced no deleterious 

 effects in the preceding experiments is because the small volumes 

 used were quickly neutralized, and are in accord with the sugges- 

 tion of Loeb ('04) that the beneficial effect of the addition of a 

 base is due, not to the effect of the hydroxyl ions, but to the 

 neutralization of acids produced by the animal. This further 

 shows that a pH of about 9 is markedly detrimental. 



