610 
wondering what it all meant. Even when 
we attempted to thread our way through 
the relatively simple tangle of the spinal 
cord, to expect that we should ever see our 
way so to unravel out the strands of fibres, 
here thick, there thin, now twisting and 
turning, and anon running straight, or so 
to set out in definite constellations the 
seeming milky way of star-like cells, so to 
do this as to make the conformation of the 
cord explain the performances of which it 
is capable, appeared to be something beyond 
our reach. And when we passed from the 
cord to those cerebral structures the even 
gross topography of which is the despair of 
the beginner in anatomical studies, the 
multiple maze of gray and white matter 
seemed to frame itself into the letters graven 
on the gateway of the city of Dis, and bid 
us leave all hope behind. 
What a change has come upon us during 
the past dozen years, and how great is the 
hope of ultimate success which we have to- 
day. Into what at the meeting at Montreal 
seemed a cloudy masss, in which most 
things were indistinct and doubtful, and 
into which’ each man could read images of 
possible mechanisms according as his fancy 
led, the method of Golgi has fallen like a 
clarifying drop, and at the present moment 
we are watching with interest and delight 
how that vague cloud is beginning to clear 
up and develop into a sharp and definite 
picture, in which lines objectively distinct 
and saying one thing only reveal themselves 
more and more. This is not the place to 
enter into details, and I will content my- 
self with pointing out as illustrative of my 
theme the progress which is being made in 
our knowledge of how we hear and how 
sounds effect us. A dozen years ago we 
possessed experimental and clinical evi- 
dence which led us to believe that auditory 
impulses sweeping up the auditory nerve 
became developed into auditory sensations 
through events taking place in the temporo- 
SCIENCE. 
[N.S. Von. VI. No. 147. 
sphenoidal convolution, and we had some 
indications that as these passed upward 
through the lower and middle brain the 
strie acusticee and the lateral fillet had 
some part to play. Beyond this we knew 
but little. To-day we can with confidence 
construct a diagram which he who runs can 
read, showing how the impulses undergoing 
a relay in the tuberculum acusticum and 
accessory nucleus pass by the stric acusti- 
ce and trapezoid fibres to the superior olive 
and trapezoid nucleus, and onwards by the 
lateral fillet to the posterior corpus quadra- 
geminum and to the cortex of the temporo- 
sphenoidal convolution. Andif much, very 
much, yet remains to be done even in track- 
ing out yet more exactly the path pursued by 
the impulses, while they are yet still unde- 
veloped impulses, not as yet lit up with 
consciousness, and in understanding the 
functional meaning ofrelays and apparently 
alternate routes, to say nothing of the 
deeper problems of when and how the psy- 
chical element intervenes, we feel that we 
have in our hands the clue by means of 
which we may hope to trace out clearly the 
mechanisms by which, whether conscious- 
ness plays its part or no, sounds affect so pro- 
foundly and so diversely the movements of 
the body, and haply some time or other to 
tell, in a plain and exact way, the story of 
how we hear. Ihave thus referred to hear- 
ing because the problems connected with 
this seemed, thirteen years ago, so emi- 
nently obscure ; it appeared so preeminently 
hard a task, that of tracing out the path of 
an ordinary impulse through the confused 
maze of fibre and cell presented by the 
lower and middlebrain. Of the mechanism 
of sight we seemed even then to have better 
knowledge, but how much more clearly do © 
we, so to speak, see vision now? So also 
with all other sensations, even those most 
obscure ones of touch and pain; indeed, 
all over the nervous system light seems 
breaking in a most remarkable way. 
