. The animals and man; an elementary textbook of zoology and human physiology. Zoology; Physiology. 362 THE ANIMALS AND MAN body in one part to a cell body in another part, or from a cell body in the cortex of the brain down to the cranial nerves or into the spinal cord, lie in or form most of the white matter of the brain. The spinal cord.—The spinal cord is an extension of the medulla oblongata. It extends from the medulla (at the foramen magnum or opening through the skull) through the vertebral cavities to the lumbar vertebras (fig. 66 B). It is slightly enlarged in the neck region and aga
. The animals and man; an elementary textbook of zoology and human physiology. Zoology; Physiology. 362 THE ANIMALS AND MAN body in one part to a cell body in another part, or from a cell body in the cortex of the brain down to the cranial nerves or into the spinal cord, lie in or form most of the white matter of the brain. The spinal cord.—The spinal cord is an extension of the medulla oblongata. It extends from the medulla (at the foramen magnum or opening through the skull) through the vertebral cavities to the lumbar vertebras (fig. 66 B). It is slightly enlarged in the neck region and again in the lumbar region. It is protected by three coats, like the brain. The cord is partly divided into halves by two deep fissures (fig. 181). In the cervical and lumbar regions the cord. Fig. 181. Diagram of a simple reflex arc. 1, sensory surface; 2, afferent nerve; 3, motor cell in gray matter of cord; 4, efferent nerve; S, mus- cle. (After Morat and Dayton.) gives off a series of spinal nerves. These occur in pairs. Each one arises from the cord by two roots, an anterior and posterior (fig. i8i). These roots unite to form the single nerve on either side. The posterior root of a spinal nerve is the sensory root, the anterior one is the motor root. The posterior root bears a ganglion, an enlargement of nerve tissue within which is found a collection of sensory nerve cells. Fig. i8i shows the relation of the gray and white matter within the spinal cord. It shows also the path of impulses from the sensory nerve ending in the skin (i) to the cell bodies in the gan- glion-and spinal cord, and from them to the muscle (5).. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Kellogg, Vernon L. (Vernon Lyman), 1867-1937; McCracken, Mary Isabel. New York, H. Holt and Company
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Keywords: ., bookcentury1900, bookd, booksubjectphysiology, booksubjectzoology
