322 THE AMERICAN NATURALIST. [VOL XXXIII. 
coming from the skin (/s), the muscles and joints (ms), the 
viscera (vs), the labyrinth (/), and from the eyes (a). All 
these sensations are combined in the cerebellum into a single 
resultant nervous impulse which influences or modifies the move- 
ments incited by the cerebrum in such a way that the codrdinated 
effect desired is attained; so that the different muscles m 
and mw contract in the proper 
manner. This may be stated 
somewhat as follows: The 
cerebellum does not —on the 
` basis of the sensations con- 
veyed to it — apportion the 
necessary stimuli to the mus- 
cles concerned in an action 
separately, but distributes it 
as a whole to the muscles 
concerned, 
In the above diagram we 
may consider the relations of 
certain sensory nerves to the 
cerebellum, as well as to the 
brium. arrows indicate the directions o $ : yates 
the nervous impulses. a, eye; g, cerebrum; tracts which receive their im- 
k, cerebellum; Z, labyrinth; 4s, ms, vs, nerves 
for impulses from skin, muscles, and viscera ; pulses from the cerebellum 
m, muscles 
and transfer them to the 
muscles, to be definitely made out. But it is still a question 
where the cerebellum exerts its regulatory influence upon our 
movements; where we have to suppose the connection, here 
represented by a dotted line, is really to be found. But there 
are also many other gaps in our knowledge of our central nerv- 
ous system; and for the object at present under consideration 
this question seems not to be of essential significance. 
It is now to be investigated how this coérdinating apparatus 
may act under different circumstances. The simplest task is 
that with which we have started out, namely, the maintenance 
of static codrdination, that is, the preservation of equilibrium 
while standing erect under perfectly normal conditions. 
If any one attempts to stand erect and perfectly motionless, 
he finds that he is unable to do so. A smoked plate has been 
