In such cases we have to seek for other evidence of disease of the brain or nerves, if any such can be traced, in actions which do not come under the power of volition ; to study the character of the patient, as it may evince nervousness, hysteria, exalted imagination, unnatural excitement or depression, and to compare one day with another the increase or diminution of symptoms. In hysteria especially, variation is the ordinary rule ; consistency, the excep tion. A patient will fail to show any power of resistance, or will bear pretty severe pinching at one observation, and at the next the symptoms have un dergone a complete change. But it is to be remembered that the different result may be due to the manner in which the investigation has been made. It has happened in my own experience, that one physician pronounced antesthesis to be complete, while another obtained distinct evidence of sensation ; because, by the one, only a transient impression was made, which was not transmitted to the sensorium, while the other maintained the irritation for some time, and at length consciousness of pain became apparent.
Where we have reason to suspect simulation or imaginary ailment, various devices must be had recourse to in abstracting the attention, in avoiding leading questions, or perhaps putting them in a wrong direction, so as to bring out a want of harmony and consistency in the tale ; we must watch the action of those muscles which are less under the control of the will, employed in winking, in speech, and in deglutition : but, besides this, we may learn much from the gait and movements of the patient, as the real paralytic makes vain efforts, which end in partial or complete failure : the •• malade imaginaire" evidently does not attempt to bring the muscles into play at all ; the will is paralysed, and not the instruments which it employs. The test of resistance which, when judiciously applied, generally serves to detect any exaggeration or imposture, is also of great value in discriminating cases in which the prac titioner is liable to be misled by a phrase employed by the patient that he has "lost the use of" a limb, when it is only motionless from stiffness or pain of the joint; just as, on the other hand, it may detect the existence of paralysis when the patient speaks of it as rheumatism.
We have no such test to apply in regard to the degree of sensibility, which must rest wholly on the.report of the individual ; but it is well to remember that it seldom exists without loss of power at the same time. Loss of sensa tion, when standing alone, except in the case of one or two special nerves, is most probably exaggerated ; but, as a sense of numbness or partial insensi bility, it may be the first indication of coming paralysis which excites the patient's notice.
The next point is to determine the form and distribution of the affection, because a knowledge of the number of muscles para lyzed, and their relations to the nervous system, is the principal element in forming a correct hypothesis regarding the seat and nature of the cause. The value of paralysis, as a symptom of disease, depends entirely on our acquaintance with the origin and course of the nerves, and on our being able to determine the point at which the interruption to volition occurs, whether by failure of the brain as the organ of mind to receive the power of the will, or of the nerve-tubes to transmit that will ; and whether the interruption, when affecting its transmission only, can be re ferred to the tract of a single nerve, or must be traced back to the common exit or origin of several. We recognize in practice three main divisions of paralysis —hemipleria, affecting one side of the body ; paraplegia, implicating both sides equally, or nearly to the same degree, up to a certain height ; and local paralysis, which may be either limited to a group of muscles supplied by one nerve, or one set of nerves, or to single muscles by themselves —in the former the disease is probably seated in the course of the nervous trunk ; in the latter, in the muscular structure.
§ 1. Hemiplegia.—This form of paralysis is distinguished by it.s limitation to the muscles on one side of the body : a line cor responding to the axis of the spinal column separates those which can no longer be called into exercise by volition, from those which retain their healthy action. In its most extended sense the one half of the tongue, the face, the chest, and the abdomen, as well as the arm and leg of the affected side, are all implicated : but such a condition rarely exists. Some of the muscles are more easily affected, some more quickly regain the power of motion ; and we seldom see a case in which hemiplegia is complete. It may, therefore, become a question, when certain muscles of one side of the body are paralyzed, whether the case should be con sidered as one of partial hemiplegia or of local paralysis. And this is not a mere question of names ; the correctness of the term employed implies a correct judgment regarding the causes of the phenomena observed ; because, if we regard it as hemiplegia, we attribute the palsy to a cause acting upon the nervous centres, and thus affecting the nerves derived from them on 9ne side ; whereas local paralysis points to a cause affecting only the nerve itself, and having no necessary connection with the central struc tures at all ; ultimately it may implicate them, primarily it is independent. The answer to the question is, in fact, the diagnosis of the case.