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1903] CHEMICAL STIMULATION m> 



Arum did not suggest that the ** respiration" might be abnor- 

 mally vigorous, as the subject was chosen for its normally intense 

 respiration. Hahn determined that a feature of the respiration 

 by the Arum sap was the rapid consumption of sugar. His 

 paper also discusses briefly the enzymes likely to be concerned. 

 So far as can now be seen, we have here a performance which 

 does not differ from respiration in the materials used, nor in the 

 products, and is stimulated in the same way by mechanical vio- 

 lence and probably by poison, but every substance concerned in 

 which passes through filter paper. 



Enough of these tables on the action of the more fatal metal- 

 lic poisons have been presented so that I anticipate that no other 

 botanist will be attracted to the field as a promising one for con- 

 clusive work on respiration, or will imagine that a control of 

 similar plants insures the validity of the results. The tap water 

 experiment was a fortunate accident, where the utmost care 

 would never have discovered the truth. It is very probable that 

 the real respiration is accelerated by these poisons. This is 

 indicated, for instance, in tables II and XV by the long contin- 

 uance of the higher rate of respiration, and it is made more 

 credible by the probably analogous action of K and Na still to 

 be described. 



The action of the poisons on the salts in the cell sap is not 

 without interest in itself. The CO^ comes ultimately from res- 

 piration; what effect freeing it may have on the respiration is 

 problematical. In the other direction, it would seem that the 

 reaction of the sap and the poison might protect the proteid, not 

 of that cell, but of others. This can hardly hold good for as 

 violent a poison as silver, but must of weaker ones, the trace 

 of which remaining in solution w^ould be harmless. Silver will 

 kill Elodea in the presence of more than its equivalent of XaCI ; 

 yet I have found that tadpoles acclimated to rather strong NaCl 

 and then thoroughly washed possess a limited immunity to sil- 

 ver poisoning. 



There is a good general parallel between the toxicity of the 

 various metals and their power to decompose carbonates, if that 

 is a proper expression for the expulsion of CO^ from the cell 



