THE INJURY CURRENT OF NERVE 
221 
also remember, at first regarded the axis cylinder as an artefact, 1 and has, until quite 
recently, stoutly resisted the attempt to consider the axis cylinder and myelin sheath 
as necessarily the possessors of different physical characteristics. Hermann has 
wrongly 2 depreciated' the importance of a dividing membrane in deciding the occur- 
ence of polarization phenomena, and in his polarization experiments the presence of 
such membranes was rigidly excluded. 4 
There are many grounds, therefore, to justify one in considering that Hermann 
did not appreciate the important part played in Grunhagen's models by the dividing 
membrane, nor the extreme probability that analogous parts were really to be found 
in the nerve. 
In Hermann's Handbook, 1879 (^d. 1? P- 234), we ^ n d the arguments which 
the propounder of the ' alteration theory ' uses to dismiss Grunhagen's theory based 
upon the assumption of pre-existing heterogeneous structures in the nerve. It is 
taken that its most decisive refutation is to be found in the manner in which it leaves 
unexplained, or badly explained, the correlated phenomenon of the action current. It 
may, indeed, be true that the particular explanation of the action current which 
Grunhagen advocated may be insufficient or even of little interest. It may be true- 
that the alterations of resistance which he invoked may not occur, nor even if 
occurring may fail to provide a direct explanation of this other phenomenon. But it 
is equally true that Herm ann's own explanation of the action current almost necessarily 
entails the occurrence of alterations of resistance, and that the failure to discover such 
alterations would also greatly militate against this. 5 
But, disregarding the particular explanation of the action current offered by 
Grunhagen, and also the possible non-coincidence ot the two phenomena of action 
and injury current, it can hardly be said that the physical structures invoked by 
Grunhagen are such as would by their arrangement prevent the development of the 
current of action ; for these are just the structures upon which now, and with a great 
shew of reason, the attempt is being made to explain this phenomenon (Boruttau, 
Strong, etc.). 6 
In the second place, Hermann uses Du Bois Reymond's 7 contra indicating 
experiment, which was undertaken by Du Bois Reymond as a crucial test of a tenta- 
tive hypothesis he temporarily advanced, and has been accorded a ' classical position ' 
by Hermann until recently. It is apparent upon consideration that this test, whereas 
1. Hermann, PJiugers Archiv., LXXI, p. 283. 1898. 
2. Nernst quoted by Boruttau, PJiugers ArcAiu,, LXXVI, p. 626. 
3. Hermann, Pfluger's Archi%\, VI. p. 342. 
4. Hermann, Nachrichten 1: ti. Gottinger Gese/I : </. JPiss, pp. 326-347. 1887. 
5. The alteration theory sees in both dying and active tissue the presence of a similar state of activity accompanied by 
a similar chemical change. If, as is most usually supposed, this chemical change involves the breaking down of complex organic 
compounds, and the separation from them of simple dissociation products, it almost certainly follows that non-electrolytes are 
broken down into electrolytes, anil so cause alteration in resistance. In fact, upon this assumption a simple explanation of both 
action current and injury current might readily be produced, the membrane by its selective influence upon the velocity of positive 
and negative ions might lead in the resulting diffusion processes to electrical phenomena. 
6. Boruttau, Strong, loc. cit. Cremer, Ztsch-vft fur Biologic, pp. 37, 550. 
7. Du Bois Reymond, 1848, Untersuchungen, I, p. 558 ; also a repetition of the same experiment for nerve, C. Morgan, 
Electrophysiolog >', p. 465. 
B 
