ON ELECTROMOTIVE PHENOMENA IN PLANTS. 283 



III. An Objection m.et. 



An objection having been raised 1 to the effect that the direct action 

 of a poison upon muscle was not necessarily of a ' physiological ' order, 

 but that it was of the same character as the arrest of action of un- 

 organised ferments, the action of aconitine upon (1) ptyaline and 

 (2) invertase was compared with its action on muscle. Aconitine, which 

 promptly abolished muscular contractility when used in n/10,000 solu- 

 tion, did not inhibit the action of these ferments in nj 1,000 and n/100 

 solution. 2 The difference shows that the action of a poison upon proto- 

 plasm must not be classified with the action of a poison upon an enzyme. 



IV. The Evolution of Hydrocyanic Acid by Laurel Leaves 

 (Prunus laurocerasus). 



The evolution of hydrocyanic acid by laurel leaves in consequence 

 of congelation or of their exposure to the action of anaesthetic 

 vapours (first pointed out by Eaphael Dubois and more recently 

 studied by Guignard and by Armstrong) affords a case where it 

 is easy to study simultaneously (a) the product of an enzyme, and 

 (b) the alterations of electrical response that take place under the 

 influence of anaesthetics. In this case, in consequence of the action 

 of, e.g., chloroform, an enzyme or enzymes of the emulsin type effect 

 the hydrolysis of a glucoside (prulaurasin), and hydrocyanic acid is 

 produced, the presence of which is readily detected by means of picrate 

 of soda test-papers (Guignard). 



Our first observations were directed to a determination of the 

 parallelism or the want of parallelism between the chemical and the 

 electrical change, regarding these two changes as the associated conse- 

 quence of the same excitatory disturbance of protoplasm by the agency 

 of the anaesthetic poison. But further observations in which a method 

 for the quantitative estimation of hydrocyanic acid was elaborated 

 indicated the insufficiency of any such simple point of view. Tbe 

 progressive evolution of HON by anaesthetised leaves immersed in 

 picrate of soda, correlated with the progressive diminution of their 

 electrical response, shows that the HCTST begins to appear as the elec- 

 trical response disappears, and that it continues to be evolved as a 

 post-mortem enzyme product long after all electrical sign of life has 

 been abolished. The electrical response is abolished in a few minutes, 

 and the abolition is final. The evolution of HON commences to be 

 manifested in a few minutes and continues actively for many hours or 

 days. 3 The relation between blaze currents and the evolution of HON 

 is dealt with in the Appendix by Mrs. A. M. Waller. 



V. Protoplasm and Water. 



The inference to be drawn from this is that the hydrolysis of which 

 hydrocyanic acid is the consequence is a sign of death rather than a 



1 Proc. Physiol. Soc., February 16, 1910. 



2 Bywaters and Waller, Proc. Physiol. Soc, June 18, 1910. 



8 A. D. Waller, ' Anaesthetics and Laurel Leaves,' Proc. Physiol. Soc., June 18, 

 1910. 



