272 



Dr. C. E. Beevor and Prof. Y. Horsley. [June 7, 



The superior laryngeal branch, on being stimulated gave rhythmical 

 movements of swallowing at the rate of seventeen times in fifteen 

 seconds, but when the nerve was cut and its peripheral end stimu- 

 lated, only very slight movement was produced in the larynx, 

 evidently by contraction of the cricothyroid muscle. 



Xlth Nerve. Accessory to Vagus. — In discussing the motor func- 

 tions of the Yllth nerve, we stated that the hitherto received idea 

 of the soft palate being supplied by the facial nerve was, according 

 to our observations, entirely erroneous. We find that the levator 

 palati is supplied entirely by the Xlth nerve.* When the peripheral 

 end of the cut nerve was stimulated inside the skull, elevation of the 

 soft palate on the same side was invariably seen. The path by 

 which the fibres from this nerve reach the palate is probably through 

 the upper branch of the pharyngeal plexus. 



Xllth Nerve. Hypoglossal. — When the entire nerve was excited 

 outside the skull, just below the point where it is joined by the 

 first cervical nerve, the tongue was flattened posteriorly on the same 

 side, and the tip protruded also on the same side, while in no case 

 was there any heaping up of the tongue. 



At the same time the depressors of the hyoid bone were thrown 

 into action, and in some cases this dragging downwards of the hyoid 

 completely prevented the tongue from being protruded. 



The movements described above were repeated without alteration 

 when the peripheral end of the cut nerve was excited at the same 

 place. 



It must be particularly noted that the movements of the tongue 

 were purely uni-lateral, and this was proved to be the case beyond 

 doubt by two experiments, in which the tongue was divided longi- 

 tudinally in the middle line to the hyoid bone when the movements 

 were seen to be entirely confined to the side stimulated. 



When the cut nerve was excited within the skull a different result 

 was obtained, the tongue was flattened behind, and protruded 

 towards the same side, but there was no action in the depressors of 

 the hyoid. 



It has always been held that the depressors of the hyoid bone 

 receive their motor nerve supply from the hypoglossal through the 

 descendens noni, but, as will be shown further on, according to our 

 observation, these muscles are supplied by the first and second 

 cervical nerves, and it is only when the hypoglossal is stimulated 

 below the point where it is joined by the branch from the first 

 cervical nerve, that any movement is produced in the depressors of 

 the hyoid. 



* I desire to add here that Dr. Felix Semon, in the course of some experiments 

 (unpublished), performed in conjunction with myself, found that in the dog the 

 levator palati was innervated by the«XIth nerve. — V. H. 



