358 RECENT ADVANCES IN SCIENCE. 



wave sweeps over a placid lake; but the Wallerian degeneration gives 

 such a view the lie direct. When we reflect that the finely balanced 

 molecular condition, which itself is nothing more than the falsely seem- 

 ing quiescence of an equilibrium of opposing motions in the ultimate 

 fibrils of the nerve twigs in the ultimate phalanx of the finger, by 

 which we touch and get to know the world without us, is dependent on 

 what is going on around the nucleus of a cell or the nuclei of some 

 cells in the ganglion or ganglia of certain upper spinal nerves, so that 

 if the continuity of the axis cylinder process be anywhere broken the 

 figure of the molecular dance changes at once and riot takes the place 

 of order. When we reflect on this it is clear, I say, that between the 

 molecules of the ultimate fibrils branching in the Malpighian layer of 

 the ball of the finger and the molecules within the immediate grasp 

 of the nucleus of the cell from which those fibrils start there must be 

 ever-passing thrills — thrills, it is true, of so gentle a kind that no phys- 

 ical instrument we as yet possess can give us warning of them, so 

 gentle that compared with them the wave which carries what we call 

 a nervous impulse must appear a roaring avalanche, but still thrills 

 the token of continued movement; and of such gentle, impalpable, 

 unnoticed thrills we must in the future take full account if we are ever 

 to sound the real depth of nervous actions. 



It is not, however, as a contribution to theoretical conceptions, but 

 rather as a method, that the results of Waller have so far had their 

 chief effect on the progress of physiology and medicine, and I have 

 chosen it as a thing to dwell on because it seems to me a striking 

 instance of the value of a method merely judged as a method, and, fur- 

 ther, because the value of its use illustrates my theme, that the success 

 of any one scientific effort is contingent on the converging aid of other 

 efforts. For some time, it is true — for years, in fact — the Wallerian 

 method was employed solely or chiefly in what, without reproach, may 

 be called the smaller problems of physiology. It settled many topo- 

 graphical questions. It cleared our views as to the distribution of 

 afferent and efferent fibers. It seemed to add or replace a few stones 

 here and there in the growing building, but it did not greatly change 

 the whole edifice. After a while, however, it met with two helpmates — 

 the one sooner, the other later — and, by means of the three together 

 we have gained and are still gaining such additions to our knowledge 

 of the ways in which the central nervous system works out the acts 

 which make up our real life as to constitute perhaps the most striking 

 progress in the physiology of our time. A wholly new chapter of nerv- 

 ous physiology has through them been opened up. 



The one colleague is to be found in the experiments of Fritz and 

 Hitzig; and of Ferrier, again, experiments on living animals— experi- 

 ments which, by demonstrating the existence of definite paths for the 

 play of nervous impulses within the central nervous system, opened up 

 paths for the play of new ideas concerning the working of that system. 



