THE CRANIAL NERVES. 77 



Extend the neck, divide the skin along the ventral 

 median line, and reflect it. Remove the heart and 

 alimentary canal, except the gullet, but leave the lungs 

 and air-passages and the oesophagus undisturbed ; cut 

 away the ventral half of the pectoral girdle, but do not 

 injure the brachial plexus (159). Ca'refully remove the 

 skin covering the hyoidean apparatus between the rami 

 of the mandible, and treat similarly the superficial mus- 

 cular layer beneath it. 



194. The anterior hyoid cornu will now readily be 

 felt through the muscles which lie on it, running par- 

 allel to the mandible on each side. At the dorsal end 

 of this cornu, and near its posterior border, will be 

 found three nerve-trunks, which are now to be care- 

 fully dissected to their peripheral distribution. 



a. One of these is the hypoglossal. It passes for- 

 ward and divides into an external branch, dis- 

 tributed to the muscles on the anterior side 

 of the cornu, and a lingual division which 

 may be traced on to the tongue-muscles, giv- 

 ing off a few filaments on its way. 



b. Near the hypoglossal, at the point where it 

 first appears in the above dissection, but lying 

 closer to the anterior hyoid cornu, the glosso- 

 pharyngeal nerve will be found ; trace it on to 

 its distribution in the space between the two 

 hyoid cornua ; one especially prominent 

 branch runs along the posterior border of the 

 anterior horn. 



c. Still another nerve will be found near the 

 proximal end of the cornu, and close against 

 its posterior border ; it is a branch of the 



