THE PERIPHERAL SYSTEM.
17. Following the analytical division, we now come to the Peripheral System of nerves and ganglia. The separation, I must often repeat, is purely artificial; but the artifice has conveniences. We separate in the same way the heart from veins and arteries, and the capillary circulation from the arterial.
Each nerve has its direct connection with a particular centre, and indirectly with the whole system. It has its circumscribed territory, and individual office. Except in a few cases of anastomosis, the action of one nerve does not involve that of another: only one muscle or one group of muscles is moved, without exciting motion in a neighbor. It is through the centres that these individual territories are united; and a wave of excitation always passes throughout the central substance. Thus the centres are not simply organs of association, consequently of regulation, but are the nexus whereby the diversity of the actions is integrated into the unity of consensus.
18. Nothing further need at present be stated respecting the nerves; but it is needful to give precision to the ideas of