THE NERVOUS SYSTEM.1
The fact that body and mind are connected so closely, and that true psychological method must proceed upon this connection, makes some preliminary knowledge necessary of the nervous system and its functions.
Nerve-elements. As far as our knowledge goes, we are able to make a twofold distinction among the elements called nervous, nerve-fibers and nerve-cells. As to what these are, the general meaning ordinarily attached to the words expresses about the amount of knowledge physiologists possess. That is, a nerve-fiber is a thread-like connection between different muscular and cellular masses. A greater or smaller number of these white thread-like fibers may unite together to constitute a "nerve," which connects an organ (muscle, gland, etc.) with a greater or smaller mass of cells. The cells, on the other hand, are microscopic elements shaped like a flask or long-necked squash. One of the necks--for there may be more than one--seems to be prolonged into the fiber, and is called the axis-cylinder process of the cell. Both cells and nerves have nuclei, small dark points which are surrounded by protoplasm. The nerves are also cut up at intervals by nodes resembling the divisions in a length of corn-stalk. See Figs. 1 and 2.
Some cells, however, are found without such connections, as far as microscopic analysis is able to go. And in many cases no direct continuity of structure has been discovered____________________