RECENT ADVANCES IN SCIENCE. 359 



I say "demonstrating- the existence of definite paths," for this, and not 

 the topographical recognition of so many centers of hypothetical nature, 

 is the solid outcome of experiments on local stimulation of the cerebral 

 cortex. Views come and go as to what is happening when the current 

 is flitting to and fro between two electrodes placed on a particular spot 

 of the Roland ic area. The solid ground on which each view strives to 

 establish itself is that the particular spot is joined by definite nervous 

 paths to particular peripheral parts. I say "demonstrating the exist- 

 ence of particular paths," but what would have been the demonstrative 

 value of the experiments of stimulation or of removal by themselves 

 without the anatomical support furnished by the Wallerian method? 

 And I may justly include within the Wallerian method not the mere 

 tracking out the degenerated fiber by the simple means at Waller's 

 own disposal, but such finer, surer search as is afforded by the later 

 help given by the newer development of the staining technique. 



They who have the widest experience of experiments on living ani- 

 mals are the first to own that in a region of delicate complexity like 

 that of the central nervous system the interpretation of the results of 

 any experimental interference may be, and generally is, in the absence 

 of aid from other sources, a matter of extremest difficulty, one in which 

 the observer, trusting to the experiment alone, may easily be led astray. 

 I need not labor the question what would have been the value of the 

 mere effects of stimulating or even of removal of parts of the cerebral 

 cortex, and whither would they have led us, had the experimental 

 results not been supported and their interpretation guided by the 

 teachings of the Walleriau method. It is not too much to say that the 

 experiments of Ferrier and his peers, brilliant as they were, might have 

 remained barren, useful only as isolated bits of knowledge, or might 

 even have led us astray, had they not been complemented by anatomical 

 facts. They have not remained barren and they have not led us astray. 

 The Wallerian method picked out from the tangle of nerve fibers mak- 

 ing up the white matter of the brain and spinal cord the pyramidal 

 tract running from the Rolandic area to the origins of all the motor 

 roots, even of the lowest, and so, joining hands with the experiment, 

 made it clear that, whatever might be the exact nature of the events 

 taking place in a particular spot of the cortex ot that area, that spot 

 was, by the definite paths of particular nerve fibers, put in connection 

 with definite skeletal muscles. The pyramidal tract was further shown 

 to be merely one — an important one, it is true, but still merely one — 

 of, a large class. So it is that the experimental results and the Wal- 

 lerian results, not merely in that Rolandic area where the results of 

 experiment take on the grosser form of readily appreciated interfer- 

 ence with movements, but in other regions where other finer, more 

 occult manifestations of nervous and psychical actions have to be dealt 

 with, are, it may be slowly, but yet surely, resolving that which seemed 

 to be a hopeless tangle of interweaving and interlacing nerve fibers 



