The comparison of the phenomena which occur in pithed or decapitated animals with the actions developed in man under these morbid states, affords most conclusive evidence as to the important question of the connection of these phenomena with the mind. In a pithed or de capitated animal we can only judge of the exercise of volition or the perception of sensitive impressions by external signs. And so far as these go we are justified in maintaining that, while the mental principle is unextinguished, it nevertheless has lost its influence over or connec tion with that portion of the cerebro-spinal axis which is separated from the encephalon. But in the human subject we have the evidence of the individual himself, who, from his own con sciousness, avows the integrity of his will and perception, but admits their dissociation from those parts of the body whose nerves are im planted in the severed portion of the cord.
Let us refer to such a case as has been already quoted. A man has fallen from a height and fractured or displaced one or more of his cervical vertebrx ; vve find the patient presenting the following phenomena. His trunk and extremities appear as if dead, ex cepting the movements of the diaphragm, while the head lives. In full possession of his mental faculties and powers, he is, nevertheless, unconscious, save from the exercise of his sight, of any changes which may affect the parts below his head, nor is the utmost effort of his will sufficient to produce a movement of any, even the smallest, of these parts. If the stun ning effect of the accident have passed off, tickling the soles of the feet will be found to cause movements, of which, as well as of the application of the stimulus, the patient is WI CO/ISCiOUS; the introduction of a catheter into the urethra, which the patient does not feel, excites the penis to erection. The limbs inay be irritated in various ways, but without ex citing any effect which the patient can per ceive, excepting movements, and these he is aware of only from his happening to see them. It is importanfto notice that, in cases of this kind, movements are difficult of excitation in the upper extremities, while they are aroused with great facility in the lower.
In these cases movements may be excited in both lower extremities by passing a catheter into the bladder. Sometimes internal changes, the precise nature of which we cannot always appreciate, but which are often the result of the irritation of flatus or other matters in the intestinal canal, excite movements in the lower or even in the upper extremities, and the patient is disturbed by cramps and spasmodic movements, more or less violent, at night. It is very remarkable, that while a patient is almost wholly insensible to external stimuli, he feels and even suffers pain from cramps of this kind.
In the hemiplegic paralysis which results from an apoplectic clot, or some other lesion affecting one side of the brain, when the para lysis is complete, the influence of the will over the paralysed side is altogether cut off, sensi bility, however, generally remaining. In such
cases it is wonderful how easily movements may be excited in the palsied leg—very rarely in the arm—by the application of stimuli to the sole of the foot, or elsewhere with less facility. The patient, who acknowledges his utter inability to move even one of his toes, is astonished at the rapidity and extent to which the whole lower extremity may be moved by touching the sole of the foot, even with a feather. It is proper to add that there is much variety as regards the extent to which these actions take place in bemiplegic cases, owing to causes not yet fully understood; still they do occur in a large proportion of instances, and in the most marked way. Their developement is frequently in the inverse proportion of the withdrawal of the power of the will. When the paralysis to voli tion is only imperfect, the effect of stimuli in exciting motions is less obvious, because of the restraining power of the will.
The cases of anencephalic foetuses may be properly referred to as affording instances of similar movements. In these beings we have no movements which can be supposed to originate in any effort of the will, nor is there any proof of the existence of sensibility. Move ments, however, of definite kind do occur under the influence of a stimulus applied to the surface.
Actions of the same kind, i. e., provoked by stimuli applied to some surface to which nerves are distributed, will continue to be manifested in animals after decapitation, not only in the trunk and extremities, but also in those segments of the former with which a portion of the spinal cord remains connected. If the body of a snake or an eel be divided into several segments, each one will exhibit move ments for some time upon the application of a stimulus. The same thing may be observed in frogs, salamanders, tintles, and other cold blooded creatures. It may be shown in a re markable manner in the male frog in the early spring, during the copulating season. At' this period an excessive developement of the papil lary texture of the integuments covering the thumbs takes place ; and this seems to be con nected with the tendency which the male frog exhibits during this period of sexual excite ment, to lay hold on any thing that is brought within the embrace of his anterior extremities and in contact with the enlarged thumbs. If the animal be made to lay hold firmly of any object, two fingers of the observer, for instance, the head and the posterior half of the trunk may be removed, and yet the anterior extre mities will maintain their grasp with as much firmness as if the animal were unmutilated. And when the frog is in full vigour, they will continue their hold for as long as a quarter of an hour or twenty minutes after the removal of the head and the posterior segment of the body. But let the portion of the cord which is connected with the anterior extremities be destroyed, and all such power of movement becomes completely annihilated.