10 
PROFESSOR B. SANDERSON ON THE ELECTROMOTIVE 
verschiebungen ” are the causes of the electrical changes observed, the proof being, 
that in general “ Wasserverschiebungen in imbibirten Korpern” are attended with 
electrical phenomena. He confesses himself unable to connect the particular phe¬ 
nomena observed with “ einzehie Phasen prevalirender Wasser verschiebungen” He 
thinks, however, that the first l( Vorschlag” is not due to Wasserverschiebung, but to 
the fact that the diffusion processes which are called into existence by the application 
of the electrodes are disturbed by alterations in the protoplasm. It is to be noticed 
that these explanations, which are contained in the concluding paragraph of the paper, 
are not in accordance with the more general statement on p. 371. In one place it is 
stated that “ all electrical phenomena are conditioned by Wasserverschiebung in 
the other, that the Vorschlag in Mimosa “ cannot be referred to Wasserverschiebung , 
but to the alteration of protoplasm which precedes it.” The difference is a fundamental 
one. 
From the preceding pages it will be seen that the two observers who have investi¬ 
gated the electromotive phenomena which are associated with the excitatory process, 
viz. : Professor Mtjnk and Professor Kunkel, have arrived at opposite conclusions as 
to their nature. According to Munk, the electromotive activity of the plant cell 
stands “ in no direct relation to the water it contains” (p. 158), It is Kunkel’s 
main conclusion that they are determined by diffusion processes. Munk gives as 
the result of his observations a complicated map of the distribution of electrical 
tension on the surface of the leaf of Dionaea (p. 40, figs. 14 and 15). Kunkel 
starts from the proposition (which he does not stop to demonstrate) that electrical 
differences do not exist at all in uninjured and untouched leaves (p. 372). According 
to Munk the electromotive properties of the leaf are referable to electromotors which 
resemble the electromotive molecules of du Bois-Reymond, with the exception that 
their signs are reversed (p. 51). This hypothesis Kunkel only mentions for the 
purpose of rejecting it (p. 371). There is, in short, but one respect, in which they 
agree. Their descriptions of the phenomena are sufficiently explicit to make it pretty 
certain that they have both witnessed the same process. As regards the physiological 
nature of the phenomena the contradiction is complete. 
PART II. 
Description of the Methods and Instruments Employed. 
The methods used in the study of the electromotive properties of an excitable living 
structure, whether of plant or animal, may be grouped under four heads according as 
they are adapted (A) for maintaining, during the period of observation, the external 
conditions of temperature, moisture, &c., which are most conducive to vigorous life; 
(B) for the investigation of the differences of tension (electrical potential) which exist 
at one and the same time between different parts of the surface of the organ; (C) for 
