﻿1903I CHEMICAL STIMULATION 95 



except in experiments in which I anticipated a tremendous evo- 

 lution of CO2. Such dilute baryta water still removes all CO^ 

 from the air. 



As subjects of experiments in this work I have used Carda- 

 mine, Callitriche, Ceratophyllum, Potamogeton, Elodea, tadpoles, 

 and fish (an immature cyprinoid, not determined). Elodea and 

 tadpoles were the subjects of extended series of experiments, 

 the other plants and the fish being used but a few times, to be 

 sure of the general validity of the results. 



In three changes of residence since doing the work with tad- 

 poles I have misplaced the detailed results of the individual 

 experiments on them. The solutions used on them were all 

 dilute enough not to be fatal during the time of experiment, and 

 their results agree in all essentials with those yielded by similar 

 work on Elodea. Single experiments with the chlorids of gold 

 and platinum on tadpoles failed to show any influence on the 

 evolution of CO^, probably because they were used in too great 

 dilution. With CoCL the evolution of CO. was accelerated. 



The other chemicals employed, Zn, Cu, Cd, and Hg, were used 

 again on Elodea. Because of this, and of the question I will 

 present shortly as to the significance of any of the results with 

 strong metallic poisons, I do not think it worth while to hunt up 

 and publish the detailed results on tadpoles. Nor will I con- 

 sume space with any considerable part of the detailed results on 

 other subjects. In the work with animal subjects, solutions 

 much too weak to kill them stimulated them to a visibly 

 increased muscular activity. This was most pronounced, with 

 relation to the toxicity of the several metals, with Cd, a little 

 less by Cu, and least of all the substances used by Pt, in 

 which the tadpoles were very sluggish, in spite of the acidity of 

 the **PtCl/' employed. It seemed to me, from a comparison of 

 the results obtained at the same time on tadpoles and on Calli- 

 triche, that the excited muscular activity of the former did not 

 produce a relatively greater evolution of CO^; from which I 

 concluded that the protoplasm of both w^as stimulated equally, 

 the plant's response being, for obvious reasons, less conspicuous. 

 A study of the acceleration of respiration would be blind 



