24 GUIDES FOR VERTEBRATE DISSECTIOX 



branches from there to other muscles and its trunk back- 

 wards. 



The ophthalmicus profundus branch of the fifth nerve has 

 already been seen forward to its entrance into the anterior wall 

 of the orbit; where does it emerge? 



The maxillaris branch of the fifth nerve passes from the 

 cranium just beneath the ophthalmicus superficialis. It soon 

 divides into a maxillaris superior which passes obliquely across 

 the floor of the orbit, and a mandibularis nerve which courses 

 straight outward at the posterior margin of the orbit. Ophthal- 

 micus profundus, maxillaris superior, and mandibularis are the 

 fifth or trigeminal nerve. Each should be traced to its distribu- 

 tion. 



One branch of the seventh or facial nerve, the ophthalmicus 

 superficialis, has already been traced, emerging from the cranium 

 along with the fifth. The other trunk passes through the cartilage 

 of the anterior wall of the otic capsule, dividing in its passage 

 so that it emerges as two branches, an anterior ramus palatinus 

 and a posterior r. hyomandibularis, the latter passing behind the 

 spiracle. Trace each as far as possible. (Lateral-line fibres of 

 the seventh, forming a buccalis nerve, accompany the maxillaris 

 superior, and others, forming a mandibularis externus, are united 

 with the mandibularis of the fifth, while fibres from the fifth 

 accompany the ophthalmicus superficialis. These, however, cannot 

 be recognized in the ordinary dissection, but are mentioned here 

 to give completeness.) 



In the otic capsule, after the removal of the membranous 

 labyrinth, note the branches of the auditory, VIII, nerve, those 

 going to the ampullse and to the central portion being the most 

 prominent. In the floor of the capsule the glossopharyngeal, 

 IX, nerve is seen running obliquely outwards and backwards 

 to the posterior lateral angle of the cranium. Cut away the 

 cartilage so as to get at the root of this nerve; also follow it later- 

 ally. To which gill-slit does it go? What happens to it then? 



In the same way follow out the vagus, X, nerve which passes 

 through the cartilage behind the ear. How many roots of origin 

 does it have? Trace it backwards, noticing its branches, includ- 

 ing those which go to the gill-slits, the one going along the lateral 

 line (lateralis nerve) and the visceral trunk, which passes back- 

 wards to the viscera (corresponds to the pneumogastric of human 



