Page:Popular Science Monthly Volume 67.djvu/329

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supplied properly by the spinal accessory. Following this in a few weeks there is some power of volitional movement in the paralyzed muscles of the face, without association of shoulder movements. Last of all comes—if it comes at all—the emotional movements over which the patient has no conscious volitional control."

This case which I have now presented in barest outline (and all similar cases of recovery of voluntary and emotional control of paralyzed muscles after anastomosis) raises a number of questions of interest to students both of cerebral physiology and of psychology from the physiological and experimental points of view. Among these the chief is, perhaps, the problem as to what takes place in the cortical centers that is brought about by the changes in the peripheral tracts through which the centers control the different groups of muscles. No completely satisfactory answer to this problem seems at present to be anywhere in sight. But there are three or four tenable hypotheses which may—probably with at least some factors taken from each—contribute toward the better understanding of the problem.

Of such hypotheses the first which I will mention suggests that a more or less nearly complete substitution of function took place between the center of the N. facialis and that of the N. accessorius. Their proximity would be favorable to this—the two centers being not more than about one inch apart. That the cortical center of the accessory nerve did exercise some control over the facial muscles through the united accessory and facial nerves is apparent from the effect produced upon those muscles by raising the arm or shrugging the shoulder. With the general fact of a certain power of substitution of new cerebral areas for disused or injured ones, cerebral physiology is familiar. But how centers so unlike in the character and variety of the muscular functions which they control as are the center for the facial muscles and the center for the trapezius muscle could substitute for each other, is difficult to imagine. Inasmuch, however, as the cortical