NERVOUS SYSTEM OF AVES. 123 



traceable, towards the myelon, from not being crossed bv a ' tra- 

 pezium.' 



The first or oplitlialmic division, fig. 49, 5, passes out of the 

 cranium by a canal situated externally to the optic foramen. It 

 is of large size, and describes in its passage through the orbit a 

 curve corresponding to the roof of that cavity ; it generally pene- 

 trates the substance of the facial bones, fig. ^^, 5*, above the 

 nasal fossa, ib. m. It divides into three branches ; the first or 

 superior is the smallest and is lost upon the pituitary membrane ; 

 the second branch is the largest of the three and the longest ; 

 it is received into an osseous canal, and terminates at the ex- 

 tremity of the beak in a great number of divisions ; the tldrd 

 branch of the ophthalmic nerve is entirely 

 distributed to the skin which covers the 

 circumference of the external nostrils. 



The second division, fig, 49, 6, or supe- 

 rior maxillary nerve, passes out of the 

 same foramen as the inferior one, ib. 7 : 

 it passes forward along the floor of the 

 orbit, and in this part of its course gives 

 oflT two filaments, of which one joins the 

 ramifications of the ophthalmic nerve, 

 the other ascends, penetrates the sub- 

 stance of the pterygoid muscles and the 

 maxillary bone, to be lost on the lateral 

 parts of the bill. In those Birds, as the re.X^'I^ororS-^r' 

 Anatidce and other Water-fowl, where 



the upper mandible is notched on the edge, each denticulation re- 

 ceives four or five nervous filaments, and the nerve is propor- 

 tionally of large size. 



The inferior maxillary nerve separates from the superior, and 

 proceeds obliquely downward, dispensing branches to the ptery- 

 goid and quadrangular muscles of the jaws ; the trunk proceeds 

 outward to the lower jaw, where it divides into two branches, an 

 internal and an external. The internal, which is a continuation 

 of the trunk, penetrates the maxillary canal, and is continued to 

 the anterior end of that mandible. In the Anatidce it gives oft^ 

 nerves to the dentations along the edge of the mandible. The 

 external branch recedes from the internal, perforates thejaAv, and 

 is distributed on its external surface beneath the tegumentary or 

 horny substance which sheaths the extremity of the mandible. 

 It supplies no gustatory branch to the tongue, which is an organ 

 of prehension, not of taste, in Birds. The non-ganglionic part of 



