328 THE AMERICAN NATURALIST.  [VOL. XXXIITI. 
nutrition. This occurs, for example, with a general loss of 
blood, anzemia, or when the loss of blood affects the brain alone ; 
in cases of this kind the symptom increases when the body is 
quickly raised to an upright position, and decreases when it is 
placed horizontally. 
In a similar manner the nourishment of the brain is inter- 
fered with by certain poisonous substances, many of which, 
such as tobacco and alcohol, especially affect the balancing 
apparatus. Thedizziness and unsteady motions resulting from 
nicotine poisoning are well known, and yet more familiar are 
the staggering movements following too free indulgence in 
alcoholic drinks. From the great similarity which exists be- 
tween these symptoms and those of cerebellar ataxia, one may 
perhaps reasonably conclude that the effects of alcohol are more 
detrimental to the processes of nourishment in the cerebellum 
than to those in other parts of the brain. 
Finally, mention should be made of numerous other circum- 
stances which may interfere with the circulation in the brain, 
and by which, again, dizziness may be caused. Here belong, 
for example, epileptic dizziness, the feelings of dizziness which 
are often observed at the beginning of acute contagious diseases, 
and many other cases. 
According to the plan which we have thus far been following, 
those derangements of equilibrium which originate in the loco- 
motor apparatus should now be considered. Here the condi- 
tions are essentially simpler. Ifa muscle which is of importance 
in standing, or a whole group of such muscles, become par- 
alyzed, the patient is no longer able to stand erect. Even a 
partial paralysis of such muscles will be sufficient to render 
standing, without external support, impossible. The result is 
exactly the same in whatever part of the locomotor apparatus 
the cause of this paralysis lies ; be it in the muscles, nerves, in 
the spinal cord, or in the brain. 
My purpose was to show you in the merest outlines how we 
are enabled through our central nervous system to maintain 
our equilibrium. But I have also had a subordinate aim; I 
wished to illustrate to you by an example the method by which 
