128). But the axons, in order to
connect with the cell-bodies, must terminate within the ganglion, so that
they too form a part of it. To some extent, also, axons pass through
ganglia with which they make no connection. The neurons in the brain and
spinal cord also lie side by side, but their arrangement is more complex
than that in the nerves and ganglia.
[Fig. 128]
Fig. 128--*Diagrams illustrating arrangement of neurons.* _A, B._ Ganglia
and short segments of nerves. 1. Ganglion. 2. Nerve. In the ganglion of
_A_ are end-to-end connections of different neurons; in the ganglion of
_B_ are the cell-bodies of di-axonic neurons. _C._ Section of a nerve
trunk. 1. Epineurium consisting chiefly of connective tissue. 2. Bundles
of nerve fibers. 3. Covering of fiber bundle, or perineurium. 4. Small
artery and vein.
The side-by-side arrangement of the neurons shows clearly the structure of
the ganglia and nerves. The nerve is seen to be a bundle of axons, or
nerve fibers, held together by connective tissue, while the ganglion is
little more than a cluster of cell-bodies. Their connection is necessarily
very close, for the same group of neurons will form, with their axons, the
nerve, and, with their cell-bodies, the ganglion (Fig.
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