178 ORIGINAL ARTICLES. 



and that glands will secrete without the intervention of nerves. It is 

 also probable that the sensorium may be stimulated without the direct 

 intervention of nerves. But it is not less certain that the ordinary 

 stimulus which awakens the activity of muscles, glands, and nerve- 

 centres, is the stimulus of nerves. Hoio this is effected we cannot say. 

 What the peculiar property of the nerves may be, baffles science. It 

 may be electricity ; it may be a correlation of that force ; it may be a 

 special " nerve-force," something sui generis. To avoid every hypo- 

 thesis, and yet to secure a specific name, I proposed the term Neu- 

 rility, as corresponding with the terms Sensibility and Contractility ; 

 the term, having met with some acceptance, may be used throughout 

 this paper. 



In the course of investigation, it appeared to me that many of 

 the vexed questions of nerve -physiology would rapidly receive answers, 

 if the perplexing ambiguities of phraseology were to give place to a 

 more rigorous nomenclature. For example, it is difficult to come to 

 an understanding respecting the motor and sensory nerves, so long as we 

 continue to talk as if we believed that "motility" resides in the spinal 

 chord, and that the posterior roots are " sensitive." Motor force no 

 more resides in the spinal chord, than explosive force resides in the 

 lighted match ; the motor-force is in the muscles, the explosive force is 

 in the gunpowder ; and when eminent physiologists are at great pains 

 to detect the " seat of motility" (siege de la motricite) in the grey matter 

 of the chord, they are perplexing a subject already difficult enough. I 

 do not assert that competent physiologists ever believe that the seat of 

 motility is elsewhere than in the muscles ; what they mean is, doubt- 

 less, that the centre, from which the stimulus issues which will excite 

 the muscles, is iii the spinal chord. But how easily the ambiguous 

 language leads to ambiguity of conception may be seen in a hundred 

 examples ; and it may be, to a great extent, avoided by rigorously de- 

 marcating the phenomena of Sensibility, Neurility, and Contractility, 

 as the actions of three different organs : nerve-centres, nerves, and 

 muscles. 



Miiller puts this question: — "Is the nervous principle, or force of 

 the motor fibres, different in its quality from that of the sensitive fibres ? 

 or are what are here called the motor and sensitive principles, actions of 

 the same nervous principle, differing only indirection — being centrifugal 

 in the motor, and centripetal in the sensitive fibres ?" Put into the lan- 

 guage of the essay, this question will run thus : — Are there two Neuri- 

 lities, one motor, and the other sensory (with the possibility of a third— 

 the secretory) ? Or does the Neuriiity in each nerve act only in one 

 direction, from a centre along the motor nerve ; to the centre along a 

 sensory nerve ? 



That there are two Neurilities is extremely improbable, nor is there 

 a shadow of evidence in its favour. Neither motions nor sensations be- 

 long to the nerves themselves, but to the muscles and centres, stimulated 

 by the nerves. It is only in the looseness of unsystematized phraseology, 

 that we speak of "sensitive impressions" being "conveyed to the 



