STRUCTURAL CHANGES DUE TO ALCOHOL 481 
The part of the brain which superintends the heart is located 
in the medulla, where a special cluster of cells sends out 
nerve fibers which enter the heart nerve. These nerve cells 
are called the heart center. 
The next nerve center to begin work is the breathing 
center, located close to the heart center, which controls the 
breathing. This does not become active until after birth. 
About a year after birth, several more nerve centers be¬ 
come active in the child’s brain. These are the ones which 
help him to walk. The cerebellum contains nerve centers 
which play an important part in walking and in learning to 
balance. The muscles which move the arms and legs are 
regulated by nerve centers in the cerebrum. 
Soon after the child learns to walk, he begins to talk and 
learn words. The several nerve centers which now become 
active are all located in the cerebrum. These are the nerve 
cells which are necessary in speaking, hearing, reading, and 
writing words. 
After the age of fifteen years the brain goes through impor¬ 
tant structural changes and the young person begins to do 
hard tasks well. It is difficult to locate the exact spots in the 
cerebrum where the nerve centers are that now become 
active, for they are widely distributed. These nerve centers 
may be called the efficiency centers and they are the last to 
develop. But as they become active, every one becomes skill¬ 
ful in respect to some one thing, although many years of train¬ 
ing are necessary before the maximum of efficiency is reached. 
The efficiency centers which are the last to become active 
and which require so much energy to train properly are the 
first to be affected by alcohol. 
367. Structural Changes Due to Alcohol. — Definite 
changes are found in the protoplasm of nerve cells after the 
use of alcohol. These consist in a shrinking of the nucleus, 
the loss of the spindle-shaped (Nissl) bodies (Figure 414), 
the swelling of the cell, and the presence of vacuoles in the 
