Electro-physiology and electro-therapeutics : showing the best methods for the medical uses of electricity / By Alfred C. Garratt.
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be found complete in the structure of the brain ; for it is now manifest that almost every structure and arrangement here found may be nearly imitated by voltaic arrangements, combi- nations, and manifestations. Muscular motion consists in a change in the arrangement and composition of tbe matter contained within the ultimate fibres, so that they become shorter, and consequently thicker and wider in diameter ; and simply tins is contraction, and this latter moves the limbs. Nerves are distributed to all the muscles ; but this supply is in a very unequal degree. The termination of the larger muscle nerves appears often to abut on many muscle fibres, and also to be in loops, running likewise transversely to the general course of the muscle fibre. Each of these muscle fibres is completely en- veloped by the minute blood vessels which run parallel with them. This admirable arrangement of the capil- laries yields the abundant supply of bright arterial blood, so necessary for the manifestation of muscular motion ; Fig. 48. a view of the Minute as contractions evidently ensue from Structure of the terminations of all Nerve-Fibrils, both to the skin, in changes taking place in the material the moscle fibres, and in the brain • f d a)jout tj ultimate fibre by Bulitttance.* J * 1. The mode of termination of nerve-fibrils in loops : three are seen to be simple; the fourth is convoluted. The latter is usually found where an exalted degree of sensa- tion exists. 2. A nerve-fibril from the brain, showing a varicose appearance, which is possibly pro- duced by traction or pressure. 3. A nerve-fibril highly magnified to show its structure — a tubular form containing the ncurine mass, consisting of cells embedded in soft granular material, which appears to serve as a simple bond of connection between them. These cells, says Dr. Druitt, vary in size from one one-thousandth to one five-thousandth of an inch in diameter. They are of a reddish-gray color, and are composed of a capsule containing a granular pulp and a true nucleolated nucleus that is adherent to the inner surface of the investing capsule. The contents of the nucleus are similar to the contents of the parent cell. 4. A nerve-cell, highly magnified, showing its composition. 5. Shows its nucleus to contain a nucleolus. 6. A nerve-cell from which several caudate processes are given off. Nerve-cells are mostly globular, but some are oval. 7. Shows the third constituent of the medullary masses, mere granules, or still more minute cells; these, in the cerebral fibres, are in greatest numbers, of different sizes and often nucleated.