1888.] On the Motor Functions of certain Cranial Nerves. 



273 



B. Spinal Division. 



Our observations of the motor functions of the first three cervical 

 nerves as regards their influence on the hyoidean muscles have been 

 made when the nerves have been excited — 



(a.) In the spinal canal. 



(b.) In the neck immediately upon their exit from between the 

 vertebral transverse processes. 



The nerves in the spinal canal were separated from the spinal 

 cord and thoroughly dried, the efficacjf of the precautions taken 

 against spread being evidenced by the difference in result obtained 

 by exciting each root. 



The effects obtained by the methods a and b were identical. 



1st Gervical Nerve. Branch of Union with the Hypoglossal. — In the 

 description of the Xllth cranial nerve, we have stated as the result 

 of our experiments that the depressors of the hyoid bone are not 

 thrown into action when this nerve is stimulated within the skull. 

 On carefully dissecting out the branch from the 1st cervical nerve to 

 the hypoglossal we find on excitation of it that there is no movement 

 in the tongue, but the depressors of the hyoid bone are strongly 

 contracted. Of these muscles the sterno-hyoid and sterno-thyroid 

 were always especially affected, while the omo-hyoid was less 

 frequently seen to contract and in some cases not at all. In the 

 cases where this muscle contracted, in one experiment the anterior 

 belly alone acted, and when both bellies contracted the movement in 

 the anterior was in excess of the posterior. 



Ilnd Gervical. Branch to the Descendens Noni. — On stimulating 

 this nerve the depressors of the hyoid were thrown into action, but 

 the muscles involved were not affected in the same way as was the 

 case with the 1st cervical nerve. The muscle which was most 

 constantly set in action by excitation of the ITnd cervical nerve was 

 the omo-hyoid and especially its posterior belly. The sterno-hyoid 

 and sterno-thyroid also took part in depressing the hyoid bone, but 

 it was especially remarked in half the cases, that their action was 

 notably less powerful than that of the omo-hyoid. In one experiment 

 in which a very weak current was employed, the omo-hyoid was 

 alone seen to contract. We are consequently led to conclude that 

 while the sterno-hyoid, sterno-thyroid, and omo-hyoid muscles are all 

 set in action by excitation of the 1st and Ilnd cervical nerves, the 

 first two muscles are relatively supplied by the former nerves, 

 while the Ilnd nerve is especially connected with the omo-hyoid 

 muscle. 



Descendens Noni. — We prefer to mention here the results of 

 exciting this nerve, inasmuch as we regard its motor fibres to be 

 derived entirely from the 1st and Ilnd cervical nerves. This nerve 



