No. 388.] MAINTENANCE OF THE EQUILIBRIUM. 323 
placed horizontally above a person trying this experiment in such 
a way that a point projecting from the cap touched upon the 
plate. Each movement of the head is then registered upon the 
smoked plate, and an irregular zigzag line is obtained as the ex- 
pression of the oscillations of the body. The sway from side to 
side amounts to one and one-half centimeters; that from before 
backwards, to two centimeters. The oscillations increase with 
fatigue and become sensibly greater if the experimenter closes his 
eyes, or if any other of the factors concerned in the process of equi- 
libration is eliminated. And the oscillations become yet greater 
in certain diseases, accompanied by the destruction of coördina- 
tion. We learn from this experiment that it is not possible for 
us to stand perfectly quiet, but that we are always balancing 
ourselves within certain limits. By this process certain muscles 
are brought much into use, and after a time they become greatly 
fatigued. Then we change our position a little, so as to bring 
other muscles into play, and at least in part to relieve those 
exerted earlier. We also learn from these experiments that 
it is more difficult to maintain our equilibrium while standing 
if any of the sensations usually participating in the process are 
inactive. Closing the eyes results in greater oscillations, and 
anesthesia of the soles of the feet, as I have already remarked, 
essentially increases the difficulty of standing. The result of a 
loss of the muscular sensations, or of the sensations from the 
labyrinth, would be still more serious, while the greatest dis- 
turbance of all occurs when several of: the component sensations 
are simultaneously wanting, especially if, as the result of disease, 
they deceive us by false sensations. 
A healthy man under normal conditions maintains his balance 
while standing in spite of the above-mentioned oscillations, and 
he is quite unconscious of this process and the attendant diffi- 
culties. But if any essential factor of the apparatus for keep- 
ing his balance be eliminated or altered in its action, he feels 
the difficulty of performing the task properly, a feeling which 
we designate as dizziness. Dizziness is the sensation of the 
loss of equilibrium combined with the feeling of difficulty in 
counteracting this loss. As will be easily understood, fear is 
often associated with dizziness. 
