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THE NERVOUS SYSTEM OF MAN 
the nerve fibers which connect the skin with the spinal cord 
and brain are called afferent (af'fer-ent: Latin, ad, to; 
fero, to carry) fibers because the stimulus always travels 
towards the brain. 
Their function is sensory, for they carry the stimulus to 
the brain. The fibers which connect the muscle with the 
brain or spinal cord are the efferent (ef'fer-ent: Latin, 
ex, from; fero, to carry) fibers, because they carry their 
message away from the central nervous system. Their 
function is to produce motion. In the special instance we 
Figure 415. — Diagram to Show Reflex Action. 
The stimulus comes in contact with the skin and is carried to the 
spinal cord. It then passes to the motor cells which carry the order 
to the muscle. The same skin stimulus goes to several other parts of 
the spinal cord. 
are studying, the heat stimulus causes the spinal cord to 
send a special message to the muscles of the finger, so that 
the latter is removed from the stove. 
This is a typical illustration of the simplest way in which 
the nervous system works, but in most reflex actions there 
are other results. After the finger has been removed from 
the hot stove by reflex action, we soon realize that the skin 
is burned, the realization coming through the smarting 
sensation. This second stimulus has been carried to the 
brain, and we are now conscious of the stove, heat, burn, 
etc. If there were no afferent nerve fibers, the individual 
could not experience any pain when hurt. 
