What portions have been removed without impairing the intellect? What is remarkable of the brain? 775. What is the influence of the brain upon the muscles? 776. What do some physiologists assert of the medulla oblongata? 777. What is remarkable of the nerves? Give the 1st observation relative to the cranial nerves. -=-=-=-=-=-=-=-=-=-=-=-= 2d. When the spinal cord is divided or compressed, as in fractures of the spinal column, all parts below the fracture are paralyzed, though the nerves leading to these parts may be uninjured. 3d. Again, one side of the body or one limb may become insensible, and the power to move it, be perfectly retained; or the reverse of this may happen--the power of motion will be lost while sensation remains. In the former instance, the function of the posterior, or sensitive column of the spinal cord on one side is destroyed; in the latter, the anterior, or motor column is affected. 4th. In some cases, both sensation and motion of one side of the body or one limb are destroyed. In such instances, both the anterior and the posterior columns of one side of the spinal cord are diseased. 778. Vigorous and controllable muscular contraction requires a sound and well-developed brain. If this organ is defective in these particulars, the movements will be inefficient, and may be irregular. The central organ of the nervous system must, likewise, be in an active condition, to induce regular, steady, and controllable muscular movements. _Observations._ 1st. Persons who have suffered from apoplexy and other severe diseases of the brain, have an involuntary trembling of the limbs, which results from a weakened state of the nervous system. -=-=-=-=-=-=-=-=-=-=-=-= To the spinal nerves. What is said of the compression of the spinal cord? Give the 3d observation relative to the spinal nerves. The 4th observation. 778. Upon what does vigorous controllable muscular contraction depend? What causes the involuntary trembling of the limbs in persons who have suffered from apoplexy? -=-=-=-=-=-=-=-=-=-=-=-= 2d. The tremor of the hand, that lessens the usefulness or incapacitates the fine artist or skilful mechanic, in the prime of life, from pursuing their vocations, may be, and is often, induced by the influence of intoxicating drink, which debilitates and disorganizes the brain. 3d. The tottering step, trembling hand, and shaking head of the aged invalid, are the results of diminished nervous energy, so that steady muscular contraction, so essential to regular movements, cannot be maintained. 779. No difference can be discovered in the structure of the several kinds of nerves in any part of their course, and the functions they are designed to perform can only be known by ascertaining the place of their origin. The nerves may be functionally divided into five groups.