360 RECENT ADVANCES IN SCIENCE. 



and cells into an orderly arrangement, of which the key is seen to be 

 that each nerve filament is a path of impulses coming* from some spot — 

 it may be from near, it may be from afar — where events are taking 

 place, and carrying the issue of those events to some other spot, there 

 to give rise to events having some other issue. 



But a third factor was wanting to forward our insight into this 

 orderly arrangement, and especially by again affording an anatomical 

 basis to open the way toward explaining what was the order of events 

 in the spots or centers, as we call them, in which the filaments began 

 or ended, and what was the mechanism of the change of events. This, 

 I venture to think, we may find in the special histological method 

 which, however much its usefulness, has been enhanced by its subse- 

 epient development in the hands of Oayal, Kolliker, and others, as well 

 as by the coincident methyl-blue method we owe to Golgi. The final 

 word has not yet been said as to the exact meaning and value of the 

 black silver pictures which that method places before us ; but this, at 

 least, may be asserted that by means of them the progress of our 

 knowledge of the histological constitution of the central nervous system 

 has within the last few years made strides of a most remarkable kind. 

 It may be that those pictures are in some of their features misleading, 

 it may be that the terminal arborization, and their lack of continuity 

 with the material of the structures which they grasp, does not afford 

 an adequate explanation of the change in the nature of the nervous 

 impulses which takes place at the relays of which the arborizations 

 seem the token; it may be, indeed it is probable, that we have yet 

 much to learn on these points. But notwithstanding this it must still 

 be said that, by the help of this method, our knowledge of how the 

 fibers run, where they begin and where they end within the brain and 

 spinal cord has advanced, and is advancing in a manner which, to one 

 who looks back to the days when Huxley was studying within these 

 walls, seems little short of marvelous. 



Let me once more repeat, the value of this silver method is not an 

 intrinsic one; it has its worth because it fits in with other methods; it 

 is available on account of what is known apart from it. I imagine that 

 if in 1842 Huxley, at Wharton Jones's suggestion, had invented the 

 silver method it would have remained unknown and unused. The time 

 for it had not then come. The full fruition which it has borne and is 

 bearing in our day has come to it. because it works hand in hand with 

 the two other methods of which I have spoken — the Wallerian and the 

 experimental methods. 



It is these three working together which have brought forth what I 

 may venture to call the wonders which we have seen in our days, and 

 I can not but think that what we have seen is but an earnest of that 

 which is to come. In no branch of physiology is the outlook more 

 promising, even in the immediate future, than in that of the central 

 nervous system. But surely I do it wrong to call it merely a branch 



