492 SCIENCE PROGRESS 



each point nearer to the pole acts as if at a higher potential 

 to points more remote ; in the kathodal extrapolar region near 

 points act as if at a lower potential than points more remote. 



Now, when an attempt is made to explain these facts, there 

 is no doubt but that we must first consider all the peculiarities 

 of the complex arrangement of electrical conductors represented 

 by the nerve-trunk. Until that is done few will listen to the 

 appeal : let us be simple, we are studying life. Physical models 

 built of materials of different conductivity have been constructed 

 to illustrate the peculiarities found. These models form a 

 physical scheme for a simplified conception of the arrangements 

 of conductors within the nerve-trunk. The inquiry is then 

 pushed further. Can electrical impulses be propagated along 

 such models ? Certainly. Well then, are we to consider the 

 nervous impulse as a phenomenon of a type akin to these? 

 Boruttau, assiduous worker upon the electrical phenomena of 

 nerve and upon such illustrative models — that is to say, an 

 examiner of both sides of this question — answers in the 

 affirmative. 



Now, before deciding the extent of the reliance we will 

 place upon this answer, we must note an important fact. 

 Nervous impulses, whatever their essential nature, are pro- 

 pagated by electrical agency. They are also propagated along 

 contiguous fibres in different directions without in any way 

 modifying one another. Nerve-fibres therefore represent 

 isolated conduction, and, as we have said, this entails electrical 

 insulation. That this insulation is by no means perfect follows 

 from the fact that electrical currents can be made to traverse 

 nerve-fibres, and also that the electrical phenomena occurring 

 within the fibre are demonstrable upon its surface. It might easily 

 be shown, however, that this imperfection as revealed in both of 

 these facts is of such a kind as to confirm the main statement 

 when put in a slightly different form. The sheaths of nerve- 

 fibres profoundly modify the motion of electrolytes. It follows 

 therefore, no matter what may be the nature of the excited state 

 of nerve, that the study of the electrical conductivity of nerve 

 must be expected to develop information such as will be gained 

 from the examination of any set of imperfectly insulated con- 

 ductors. The core-model can be foreseen, and its invention 

 cannot be at once accepted as revealing essential facts. It is not 

 enough to have become acquainted with the insulation of the 



