THE INJURY CURRENT OF NERVE 
225 
It has been stated previously (see note, p. 221) that a 'core model' structure (such 
as was assumed by Grunhagen) might be used to explain the electrical phenomena 
of the 'action current,' even if they were the secondary consequences of chemical 
change taking place in the axis cylinder. This possibility has been considered by 
Boruttau, forming, as it does, one of the two only probable lines upon which this 
phenomenon can be investigated and perhaps explained. But he has taken a greater 
interest in the other possible explanation, and has sought confirmative suggestions 
from experiments upon 'core models,' and has also sought confirmatory facts from 
experiments upon nerve. 
According to this second explanation, the nerve has not only a core model structure, 
but also that structure is just of the kind required to act as the purely physical 
conductor of electrical change, and to conveniently transmit energy from point to 
point without involving the development of new sources of energy (chemical changes) 
in its line of progress. Such a conception of the arrangement of structures in the 
nerve has also been frequently debated since the date of Galvani's discovery. The 
possibilities of the insulating or semi-insulating sheath of the nerve, that is to say of 
the core model structure of the nerve, have been discovered from every point of 
view, but without any very direct attempt having been made to obtain experimental 
data which might place definite limits to these possibilities. 
Boruttau and Strong,' and perhaps Hoorweg (although his methods of 
illustrating his conception are open to objection), have realised the necessity entailed 
by the core model structure, namely, that its fracture must provide one with a 
current of injury. Strong has presented a detailed description of his hypothesis, 
and Boruttau has illustrated a similar one by a working model, 1 but neither 
seem to have grasped the important corollary which their statements, if true, must 
entail, namely, that the injury current and its modification, under known conditions, 
may, or rather must, give valuable information as to the details of the core model 
structure. 
The appreciation of this position necessitates a return to Du Bois Reymond's 
point of view and the establishment of the injury current as a phenomenon of primary 
importance. 
Notk on the Purely Physical Theory of Nerve Function 
The greatest objection to a physical theory of nerve function is the existence of recorded instances in 
which the transmission of the nervous impulse is proved to have taken place unaccompanied by a demon- 
strable physical phenomenon. Man} - of these instances are open to considerable suspicion, as are alj 
physical experiments made by investigators satisfied with approximate and inexact methods and apparatus. 
Criticism of such recorded instances has already been undertaken by Boruttau, but there are certain broad 
principles affecting experiments of this kind which have not been as much insisted upon as is necessarv. 
1. Strong, Journal of Physiology, XXV, p. 42-. 
2. Boruttau, Pfliigers Archii: LXIII, p. 1^4. 1X96. Gelatine cylinders ot K.C1. solution surrounded by a mantle of 
•6 per cent. NaCl. solution. The model so formed shews a negativity of cross section to longitudinal surface. 
