Motor disorders: paralysis, paresis, hemiplegia, crossed hemiplegia, spinal hemiplegia, paraplegia, monoplegia, local palsy, pseudo-paralysis, spasm,—tonic,—clonic, tremor, hemispasm, monospasm, spasm of eyeball, spasm of head, paraplegic spasm, general spasms—convulsions, local spasms. Incoördination. Staggering. Reflex action. Morbid reflex: increased reflex, reflex tonic spasm. It seems desirable to note specially some of the more prominent morbid nervous phenomena and conditions, with lesions or other conditions which cause them, before considering what are usually recognized as special diseases. MOTOR DISORDERS. =Paralysis= (_Akinesis_) is loss of voluntary or involuntary muscular movement through defective innervation. =Paresis= is a paralysis which is partial in degree; power of motion is impaired but not completely lost. =Hemiplegia= is the loss of voluntary motion in many muscles on one side of the face or body. In general hemiplegia, the following muscles are usually excepted: muscles of the tongue, of mastication, of the eye, of respiration, of the neck and trunk, generally and of the proximal part of the limbs. The hind limbs are usually most affected, and muscles that are most exclusively under the control of the will those dominated by the cortical centres of the brain. When due to a clot on the brain or degeneration it occurs on the side opposite to that occupied by the clot, on account of the motor fibres crossing at the anterior pyramids of the medulla. Hemianæsthesia is a rare attendant and when present is often on the side opposite to the hemiplegia. Sensory fibres cross in the spinal cord, and the lesion is probably spinal. =Crossed Hemiplegia= is motor paralysis of certain cephalic nerves (3d, 7th, 5th, 6th, and 8th,) on the same side with the clot or lesion, and of the muscles of the trunk on the other side. The cranial nerves proceed to muscles on the same side as their origin, while filaments going to the trunk through the spinal cord, cross in the pyramids (motor), or spinal cord (sensory). In crossed hemiplegia, hemianæsthesia is common with both forms of paralysis on one side. =Spinal Hemiplegia= has the face and head sound (except sometimes the iris), and half the body paralyzed on the side opposite to that on which the spinal lesion (clot) exists. If anæsthesia exists it is on the side opposite to the lesion and posterior to it—the sensory filaments crossing just before leaving the cord. =Paraplegia= is loss of voluntary power of one transverse half of the body; usually the posterior, and affects the tail, and has coincident anæsthesia, being due to a spinal lesion. Anal and vesical sphincters may or may not be paralyzed according as the lesions implicate their respective spinal centres or not. If there is neither anæsthesia nor vesical paralysis the lesion may be cerebral, in the paracentral lobes of both hemispheres (meso-vertix at the fissure of Rolando).