6 
PROFESSOR B. SANDERSON ON THE ELECTROMOTIVE 
Professor Munk’s explanation of the excitatory variation is, of course, in conformity 
with his doctrine of the electromotive activity of the individual cell, which has been 
already explained ; namely, that each parenchyma cell has the endowment of a cylin¬ 
drical electromotive element of which the poles are positive to the middle,* and the 
excitatory change produced in each cell consists in increase or diminution of the 
electromotive force of each cell. If the variation consisted of a single phase, it might 
he accounted for by supposing that all the cells of the parenchyma of the lobes are 
affected by excitation in the same way. As, however, it presents the characters of a 
“ DojopelschwanJcung” — i.e., consists of two phases succeeding each other, of opposite 
signs, this must be accounted for either by supposing (1) that all the electromotive 
elements in the structure are similarly affected, but not at the same time, the excita¬ 
tory change being propagated from the seat of excitation in such a way that it first 
affects the electromotive elements at one contact, then those at the other; (2) that all 
the electromotive elements are similarly affected at the same time, changes of opposite 
signs following each other in each element simultaneously ; (3) that there exist in the 
structure two sets of electromotive elements, which are affected in opposite directions 
by excitation, the disturbance reaching its maximum in the one set later than in the 
other set. 
Of these three alternatives only the third appears to Professor Munk admissible. 
The first he rejects on the ground that if it were true the character of the excitatory 
variation would be affected by the seat of excitation. This he finds not to be the 
case. Thus in Exp. II. (see Table) the effect should be different according as the leaf 
is excited by touching the proximal or distal hairs. According to Professor Munk 
there is no difference (p. 136) either in this or other similar cases. He therefore 
concludes that the “ Bojypehchwan'kuncf is not due to propagation of the excitatory 
effect from the seat of excitation. “ Danach kann weder die complicirte Schwankung 
in irgend einer Beziehung zum Orte der Beizung stehen, noch kann iiberhaupt von 
diesem Orte der Erfolg der Beizung, innerhalb der Genauigkeitsgrenzen unserer 
Untersuchung, irgendwie abhangig sein” (p. 138). The second alternative is rejected 
on the ground that in IV. (see Table) the Yorschlag, if it occurs at all is very incon¬ 
siderable, and is very frequently absent, consisting of one phase only, which could not 
be the case if each cell underwent first a diminution then an increase of its electro¬ 
motive force, and all acted simultaneously. The third alternative, thus adopted by 
exclusion, viz.: that the two sets of electromotive elements are oppositely affected by 
excitation, serves, Professor Munk thinks, to explain the characters of the excitatory 
effect in all the cases observed by him. 
* Die ohngefahr cylindriscben Zellen des B1 attfl tig el - Par encby m s und der beiden Mittelrippen- 
Parencbyrae sind mit Kraften ausgestattet der Art, dass die positive Elektricitat von der Mitte der Zelle 
nach jedem der beiden Pole hingetrieben wird, die Pole positiv sind gegen die Mitte” (p. 97). 
