﻿1903] CHEMICAL STIMULATION 175 



Both lodin and antipyrin accelerate the evolution of CO^ 

 from the Elodea, but not from the tap water. Their action must 

 be on the the protoplasm. The acceleration observed was a 

 shade greater than Jacobi's result with the same substances. 



An experiment with potassium cyanid may be inserted here. 



The reason for performing it was the regard in which KCN is 



held by animal physiologists as a substance inhibiting respira- 



tion. The evidence for this rests, largely at least, on its pre- 



I venting the consumption of oxygen, so that in KCN poisoning 



the blood retains its arterial color (its other effect in interfering 

 with the carrying of the O by the blood being irrelevant here). 

 I have made two tests of the evolution of CO3 under the influ- 

 ence of KCN, one of which is reported here. Neither of them 

 has the measure of quantitative exactness I could desire, but the 

 apparent acceleration was so great it is hardly possible that it 

 should have been an error. 



TABLE XXXII. 

 January 22. Test of KCN. No contro]. 



====== The alkalinity of KCN prevented 



Time Experiment the escape of more than a trace of 



10:54-3:54 



3:54 iL KCN 



100 



3:56-4:56 



COjj. To determine the CO3 then the 



0.048 KCN solution was made slightly acid 



in bottle. '^^'^^^ HgSO^, and the CN precipitated 



with AgNOg. It was then boiled. 



Total CO2 - - - o.899«N. 



As a control, 400<== KCN (same solution) treated in same way. The CO, from 



100 

 It was - - - . . 0.20S" N, 



or for soc^^ . . . 0.260, leaving as the COg from respiration in the 



experiment - - . . o.bT.ff" N. 



This result, with the evidence that oxidation is hindered by 

 KCN, suggests forcibly that it is a substance which acts on 

 "normal" but not on "intramolecular" respiration, which would 

 amount to a proof for the already well supported theory that 

 the evolution of COg and the taking on of O are distinct activi- 

 ties of the plant; the latter, when it occurs, being dependent on 

 the former, instead of vice verm. The action of KCN will well 

 repay more study, whatever it may show, but I have had no 

 time to follow it up. 



