Ebook: Principles of Physiological Psychology

General Books publication date: 2009 Original publication date: 1904 Original Publisher: Sonnenschein Subjects: Psychophysiology Psychology, Experimental and physiological Notes: This is a black and white OCR reprint of the original. It has no illustrations and there may be typos or missing text. When you buy the General Books edition of this book you get free trial access to Million-Books.com where you can select from more than a million books for free. Excerpt: CHAPTER II Structural Elements of the Nervous System § 1. Morphological Elements The nervous system is made up of three kinds of morphological elements : (1) cells of peculiar form and structure, the nerve-cells or ganglion cells; (2) fibrous structures, originating as outgrowths from the cells, -- the nerve- fibres ; and (3) a ground-reticulum, which in places is finely granular and in places fibrillar, and which consists of the terminal ramifications of the nerve-fibres and processes of the nerve-cells. To these must be added (4) a sustentacular substance, fibrous or amorphous in structure, which is regarded as a form of connective tissue.1 The nerve-cells, with the fibrillar ground-reticulum that surrounds them, are essential constituents of all the central parts. In the higher nervous centres, however, they are restricted to definite areas, which, partly from their rich supply of capillary blood-vessels and partly from the presence of pigment-granules, collected both in the protoplasm of the cell-bodies and in the ground- reticulum, possess a darker coloration than the surrounding tissue. This grey substance contrasts so sharply with the white or myelinic substance that the distribution of cell-groups through the central organs may readily be followed by the naked eye. The myelinic substance itself owes its peculiar character mainly to the myelinic sheaths which enclose the nerve- fibres issuing from the grey substance. The connective tissue cement- substance occurs in three principal form...