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That is to say, that in attempting to decide between the two theories, the alteration 
theory and this pre-existence theory, he does not place them in clearly alternative 
positions, but considers the second as a corollary to the first. No proofs have ever 
been produced of the existence of a dying condition at the cut end of a nerve or 
even of a localised chemical change. Both may, indeed, exist, but the primary reason 
tor considering the possibility of such a state is that Hermann propounded the 
alteration theory. Hermann is, therefore, considering the pre-existence theory from the 
point of view of the teachings of the alteration theory, and not as a quite separate and 
distinct possibility, and must have done so from the first. 
The general impression left upon one's mind is that Grunhagen's theory has 
never met with the consideration nor with the acute criticism which it deserved as a 
logical deduction from a valuable appreciation of the relative values of the structures 
of the nerves. 
Note 
Grunhagen's theory in its most acceptable form was completely anticipated by Buff in 1854, although 
applied to electrical currents obtainable from plant tissues, and not from muscle or nerve. (Ann. d. Chemi. 
u. Pharm., Bd. 89, 76. 1854.) The currents obtained were explained as the result of — 
(1) A negativity of the sap ; 
(2) A positivity of the surface water ; 
(3) A sharp delimitation of the two solutions by the epidermis. 
Buff also supported his conclusions by physical experiments of interest. 
Jurgensen, in 1 86 1, also working with plants, came to very similar conclusions supported by similar 
experiments. (Studien. d. Physiol, lnsthut. zu Breslau, I, 87-109. Leipzig, 1861. 
J. Reinke, in 1882, also discussing plant currents, refused to admit an explanation couched in terms 
of vital states, and anticipates a possible explanation in the complex arrangement of moist conductors con- 
tained in plants. (Pfliigers Archiv., XXYHI, 143, 1882.) 
J. S. Macdonald, in 1 900, produced certain evidence obtained from mammalian nerve, and considered 
this to be in support of a similar theory. 
Buff's and Jurgensen's conclusions were adversely criticized by Hermann in 1871. He also criticized . 
the value of their physical experiments, performing similar experiments with uncertain results. The value 
of Buff's, Jurgensen's, and Grunhagen's physical experiments are, however, now easily assessed by an 
appeal to the new subject of electrochemistry. (Hermann, Pfliigcr s Archiv., IV, p. 148, 1871. 
Section IV. Boruttau 
Du Bois Reymond used the current of rest as a phenomenon from which to 
extract a practical conception of the physical structures of the nerve, and proceeded 
with this structure in his mind to explain the other electrical phenomena which could 
be demonstrated in it. Boruttau has used the polarization phenomena in a similar 
manner. The polarization phenomena entail a ' core model ' structure for the nerve, 
and have been held to do so by several investigators. Granted the ' core model ' 
structure of nerve, all the other electrical phenomena of nerve are stated as explained 
by it. 
