The protoplasmic processes called _dendrites_ have a similar structure to the cell body. The dendrites branch dichotomously, become rapidly smaller, and usually end at no great distance from the cell body. The _axone_ or _axis cylinder process_, differs from the cell body and from the dendrites. It does not contain chromophilic granules. It consists entirely of neurofibrils and perifibrillar substance. It emerges from the cell at an enlargement known as the axone hill. This hill is free from chromophilic bodies. Nerves are divided into two kinds, medullated and non-medullated. _Medullated nerves_ are divided into two kinds: medullated nerves with a neurolemma, and medullated nerves without a neurolemma. Medullated nerves with a neurolemma consists of an axone, a medullary sheath, and a neurolemma. A delicate membrane called an axolemma, or periaxial sheath envelops the axone. The medullary sheath called myelin, is semifluid, somewhat resembling fat. The outer covering is the neurolemma, or sheath of Schwann. It is a delicate, structureless membrane which incloses the myelin. There is under this sheath an occasional oval nucleus. At intervals there are constrictions, or nodes, called the constrictions of Ranvier. The part between the nodes is called the internode. The medullated axones without a neurolemma are the medullated nerve fibers of the central nervous system. The non-medullated axones, or _non-medullated nerve fibers_, are divided into non-medullated axones with and those without, a neurolemma. The non-medullated axone without a neurolemma is merely a naked axone. They are confined to the gray matter and to the beginnings and endings of sheath axones, all the latter being uncovered for a short distance after leaving the nerve cell body and also just before reaching their terminations. The long axones serve to make connections with the peripheral, or distant, nerve cell, muscle cell, or gland cell; while the shorter axones of certain neurones divide into terminal branches in the immediate vicinity of its cell body, presumably to come into relation with other nerve cells in the same or adjacent groups. [Illustration: FIG. 77.—Histological structure of tissues. 1. Non-striated or involuntary muscle cell. _a._ 1, Nucleus; 2, Protoplasm. _b._ Transverse section showing nuclei in the center of the cells that are cut through the nuclear zone. _c._ A cross-section of the connective tissue which binds together the muscle cells. _d._ A section showing the so-called intercellular bridges. 2. A cross-section of the rectus abdominalis. 1, The endomysium which binds the cells into primary fasciculi or bundles. 2, The perimysium which surround the bundles of fasciculi. 3, The epimysium which surrounds the muscle. These binding structures are white fibrous connective tissue.