Page:Mind (Old Series) Volume 12.djvu/443

 430 W. L. MACKENZIE : haps the chief objection to " sense," strictly taken, arises from the doctrine of the " out-going current " commonly associated with " muscular sense ". This at least is the impression one gets from reading the recent discussion at the Neurological Society, where the chief dividing question was as to " in-going" or " out-going " current. But clearly one may ask if there is a. sensibility of muscle, without committing oneself to any doctrine of "in-going" or "out-going" nervous current, and this M. Beaunis (Revue Philosophique, March, 1887) has done in an in- genious experiment. To determine whether the sensibility called muscular is to be attributed to the muscles themselves or to the skin and neigh- bouring parts, M. Beaunis experimented on the larynx. The movements of the vocal cords in singing are remarkable for their delicacy and precision, and differences of tension in these cords reckoned by fractions of a millimetre influence in a perceptible way the accuracy of the sound. There are two possible sources of guiding sensibility : first, the mucous membrane of the larynx ; second, the muscles. These M. Beaunis proposed to separate by paralysing the sensibility of the mucous membrane. " If the voice remain accurate, then the sensibility of the mucous mem- brane does not regulate the differences in tension of the vocal cords. These differences, therefore, can be regulated only by the muscles of the cords. Therefore there is muscular sensibility. If the voice become false . . . then the sensibility of the mucous membrane intervenes ; there is no true muscular sensibility ; the muscular sense does not exist. Finally, it might happen that the voice, without becoming altogether false, showed a certain change, more or less marked, in accuracy. In this case both would be involved at the same time in graduating the tension of the cords the sensibility of the mucous membrane as well as the muscular sensibility." To paralyse the laryngeal mucous membrane M. Beaunis employed cocain. He secured as a subject a practised singer, familiar with laryngoscopic examination and intelligent enough to analyse his feelings and grasp the import of the experi- ment. He first made the subject a tenor sing, without accom- paniment, a pretty long air of moderate difficulty ; the emission of sound was good, the voice accurate and of good quality. He next applied to the vocal cords with a brush a solution of cocain. The subject then sang the same air, first three minutes, then eight minutes, after the application of the cocain. The singing was less satisfactory than at first ; the quality was less mellow, the sound less pure. But in accuracy the voice was the same. Laryngoscopic examination at this stage showed the edges of the true vocal cords pale, and on them some small masses of mucus. When the action of the cocain was exhausted, M. Beaunis applied a solution stronger than is usually applied to the larynx. With this the lips of the glottis became pale, for the small vessels of the mucous membrane were contracted. The subject then began the same air again, first three minutes, then six minutes, after the