The varieties of paralysis, in %bleb single and small portions of the body are affected, do not in general continue permanently limited to the part first attacked, but are often precursors of the more general affections already described. The most important forms, and those in which the paralysis mod frequently remains fur a long time local, are those in which the eyelids or muscles of the eye, and those in which the muscles of the face, are affected.
In paralysis of the muscles of the eye, the most commonly affected are the elevator of the upper eyelid and the orbicular muscle of both the eyelids. When the former loses its power, the eyelid drops, and the eye is constantly more or leas closed ; when the latter is affected, the eye cannot be shut, and reznains permanently wide open. The dropping of the upper eyelid (or Weis) is dependent on a disease or Injury of the third pair of nerves, and is usually accompanied by a paralysis of eome of the unmans of the eyeball which are supplied by the same nerve; so that the position of the eye is altered, or it cannot be freely moved. The permanent openness of eye is the result of disease of the seventh or facial nerve, or of its branch supplying the orbicular muscle ; sometimes this latter branch alone is implicated ; but more frequently the whole trunk is affected, and there is coincident paralysis of all the muscles of the face. As far as regards their influence on vision, both cases are almost equally injurious; the first by placing a veil constantly over the front of the eye; the second by destroying the power by which particles of dust, itc., are removed from the sur face of the eye, and thus leaving it exposed to the dangers of constant irritation and inflammation.
In paralysis of the face many different conditions are observed, according to the nerve which has been diseased or injured. The sensation of the face depends entirely on the sensitive or larger portion of the fifth pair of nerves [Thum in Nat. HisT. the motion of its muscles on the seventh or lacial nerves, and the motion of the muscles of mastication on the motor or small portion of the fifth pair. Now if either of those three nerves or their sources in the brain be separately injured, the paralysis will be limited to a loss of sensation, a hues of the motion of the muscles of the face, or a loss of the motion of those of the jaw, on the side affected. In the most frequent awes of
affection of the fifth nerve, both its sensitive and motor portion are injured, and there is both n loss of motion of the muscles of the jaw and a loss of sensation of the whole of the skin of one aide of the face.
Lastly, a limb, or a part of a limb, or a single muscle or set of muscles in any part of the body, may be paralysed. In some cases such an affection is only s sign of disordered digestion, and thus they occur chiefly in children ; in others it exists in what is called general nervousness, as in hysterical women, who, with many other strange disorders, sometimes lose the power of swallowing or speaking. Most frequently, however, these forms of local paralysis depend on injury of the nerve' of the part, which are compressed by tumours or involved in some diffused disease.
An important class of local paralytic affections includes those in which recent investigations have detected the sources of many cases of congenital or acquired deformity, such as club-foot, curvature of the :pine, squinting, Ac. In these, one or more muscles of a limb or organ being from birth or from childhood weak or powerless, its antagonist muscles draw the part into an unnatural position, and hold it there firmly and permanently fixed. One of the most important achieve ments of modern surgery is the cure of these affections by the division of the contracted muscle or its tendons. [CONTRACTION,' Throe, however, are the only cases in which general rules of treat ment can be laid down. The varieties of causes from which paralysis may arise, afford sufficient evidence that its treatmeut in different cases must vary greatly. It cannot indeed be said to boa disease of itself, since it is only a sign of some disorder of the nervous system, which is often seated at a distance from the part whose motion or sensation is lost. This disorder, also, is of no definite kind, but may be the result of haemorrhage, or inflammation, or slow structural change of the nervous substance; or it may be produced by the pressure of fractured hones, or tumours, ke. In each Lase, therefore, the cause of the para lysis must be treated before there can be any expectation of removing its effects.