Publication Date: 2013-09-13 | ISBN-10: 123697154X | ISBN-13: 9781236971548
This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1906 edition. Excerpt: ... Nervous System. The main sympathetic trunk of each side extends forwards in front of the first ganglion, and enters the skull at the foramen in the exoccipital bone through which the glossopharyngeal and pneumogastric nerves pass out: it is connected with the pneumogastric nerve, and then runs forwards within the skull to the Gasserian ganglion of the trigeminal nerve, in which it ends. 0. Histology of Nerves. Nervous matter consists histologically of elements of two kinds, nerve cells and nerve fibres. The nerve cells are branching nucleated cells, connected by their processes with one another and with the nerve fibres. The nerve cells are the centres whence impulses originate, while the nerve fibres serve to convey these impulses from one part to another. A local accumulation of nerve cells is called a ganglion. 1. Nerve Fibres are of two kinds, medullated and nonmedullated. a. Medullated nerve fibres form almost the whole of the cranial and spinal nerves, and a large part of the brain and spinal cord. Take a smalt piece of the sciatic or some other nerve from a freshly killed frog: spread it out and tease it in a drop of normal salt solution: examine with low and high powers: note i. The nerve fibres: unbranched. ii. The perineurium, or connective tissue binding the nerve fibres into bundles, or "nerves." In each nerve fibre note iii. The primitive sheath, or sheath of Schwann: a very delicate external investment, seen with difficulty, and only in certain places. iv. The medullary sheath: a thick fatty layer within the primitive sheath; it is highly refractive, and gives the nerve fibre its double contour. Tease in glycerine a small piece of nerve that has been treated with osmic acid: examine with the high power a single...
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