THE NERVOUS SYSTEM. 69- 
thus, each of the nerves of special sense—for example, taste, smell, &¢— 
has its own proper centre. The most prominent part of the brain is the 
cerebrum,’ or, as it is also called, the cerebral hemispheres (because it is 
divided into two by a deep fissure from front to back), which, on the 
outside, presents the appearance of a piece of cloth crushed together in 
irregular folds. On the outside is a coating of gray matter, while in the 
inside is white matter. Behind and beneath the 
cerebrum is the cerebellum, or little brain, which is 
also divided into two hemispheres, and which is 
specially charged with the regulation of movements. 
From the brain, and through openings in the skull, 
proceed a number of nerves to the different organs 
about the face; and as these organs are for the most 
part double, the nerves go in pairs; thus, a pair of 
olfactory,” or smelling nerves, go to the nose, a pair of 
optic,> or seeing nerves, go to the eyes, and a pair of 
auditory, or hearing nerves, to the ears. Besides 
these pairs, there are nerves to the organs of taste, and 
a number of others both afferent and efferent. 
From the base of the cerebellum, the spinal cord 
passes down through the middle of the series of verte- 
bree forming the spine, sending out nerves to the 
trunk and limbs; and its principal function is to 
connect these nerves with the brain, although it has 
also influence of its own not dependent on the brain. 
The nerves springing from the spinal cord are all in 
pairs, arising between each pair of vertebrae, one on 
each side. The manner in which neryes are supplied 
to the extremities is through what is called a plecus,5 
or network. Several nerves spring from the spinal 
cord, and proceed together for some distance without 
meeting ; they then divide, and branches from differ- 
ent nerves unite to form new nerves, and these again 
divide, and interchange fibres; and the nerves thus 
formed proceed to the extremity, as seen in fig. 58, 
which represents the nerves of one of the arms. 
Besides the system of nerves just described, there is 
another set of nerves and ganglia in the body. There is Fig. 58, 
a chain of ganglia, connected by nervous cords running 
down in front of the spine, which sends ‘off nerves to the viscera and 

1 From Greek kara, the head. 2 From Latin olfactus, the sense of smell. 
3 From Greek optos, seen. 4 From Latin audio, to hear. 
5 From Latin plecto, plerum, to twist or knit. 
