*Side-by-side Connections.*—On separating the ganglia and nerves into their finest divisions, it is found that the nerves consist of axons, while the ganglia are made up mainly of cell-bodies and dendrites. The axons lie side by side in the nerve, being surrounded by the same protective coverings, while the cell-bodies form a rounded mass or cluster, which is the ganglion (Fig. 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. 128). *End-to-end Connections.*—These consist of loose end-to-end unions of the fiber branches of certain neurons with the dendrites of other neurons. The purpose of such connections is to provide the means of communication between different parts of the body. There appears to be no actual uniting of the fiber branches with the dendrites, but they come into relations sufficiently close to establish _conduction pathways_, and these extend throughout the body (Fig. 129). They connect all parts of the body with the brain and spinal cord, while connections within the brain and cord bring the parts into communication with each other. [Fig. 129] Fig. 129—*Diagram of a nerve path* starting at the skin, extending through the spinal cord, and passing out to muscles. A division of this path also reaches the brain.