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Thus, when the cord is divided at any point, compressed, as by a tumor or broken bone, or disorganized by disease, the result is a complete loss of sensation and voluntary movement below the point of injury. If by accident a man has his spinal cord injured at some point, he finds he has lost all sensation and power of motion below that spot.
What ones contain both afferent and efferent fibers? In what respects is the nervous system similar to a system of telephony? In what respects is it different? Observe the convolutions of the cerebrum and compare these with the parallel ridges of the cerebellum. Observe the appearance and general distribution of the nerves and their connection with the brain and spinal cord.
Running downward from the base of the brain, like the stalk of a flower, is a great bundle of nerve-fibres, the central cable of our body telephone system, the spinal cord.
In the medulla are placed offices or centres which regulate the vital operations carried on by the heart and by the lungs. It has also to serve as a passageway for thousands of delicate gossamer-like nerve fibres passing from the brain, which fills the whole chamber of the skull, to the spinal cord, situated in the canal of the backbone.
A moving structure, as a wagon or a bicycle, has within it some strong central part to which the remainder is joined. The same is true of the skeleton. That part to which the others are attached is a long, bony axis, known as the spinal column. Certain parts, as the ribs and the skull, are attached directly to the spinal column, while others are attached indirectly to it.
The central portion comprises the brain or encephalon and the spinal cord. These organs are lodged in the cranial cavity and spinal canal. The nerves and ganglia comprise the peripheral portion. The nerves form white cords that are made up of nerve fibres.
She connects the nerves in their passage from the brain and the spinal cord through the body with manifestations of life. She has a series of chapters with regard to psychology normal and morbid. She talks about frenzy, insanity, despair, dread, obsession, anger, idiocy, and innocency.
In the upper smaller tube the spinal marrow and brain are fashioned; in the lower, the alimentary canal and heart; and at length two pairs of buds shoot out at the sides of the body, which are the rudiments of the limbs. Slowly and gradually these changes take place.
The vaso-motor nerves have their governing centre in that upper portion of the spinal cord which is within the skull, the so-called medulla oblongata. When the spinal cord is divided, the vessels are cut off from the influence of this vaso-motor centre, and at once dilate, profoundly affecting the blood-current by doing so.
Experiment also proves that if only the posterior root of a spinal nerve be cut, all sensation is lost in the parts to which the nerve passes, but the power of moving these parts is retained. But if the anterior root alone be divided, all power of motion in the parts supplied by that nerve is lost, but sensation remains.
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