Nos. IAXD2.] AX ATOMY OF SCOMBER SCOMBER. 233 



dorsal portion of the membranous interorbital septum. In this 

 part of its course it is closely pressed against its fellow of the oppo- 

 site side of the head, and is oval in section, the long axis of the 

 oval being directed vertically and being about twice as long as the 

 transverse axis. The base of each nerve is considerably enlarged, 

 as already stated, and is often somewhat rounded as if there were 

 here a ganglionic formation, an appearance too strongly marked 

 not to have especial attention called to it. 



At about the middle of the orbit the olfactory nerve, on each 

 side, turns laterally, pierces the corresponding half of the mem- 

 branous interorbital septum and reaches the lateral surface of that 

 structure. Turning slightly downward and laterally it continues 

 its forward course, running dorsal to the obliqui muscles at their 

 origins, and reaches the posterior opening of the olfactory canal 

 through the antorbital process. Traversing that canal it issues, by 

 its anterior opening, into the nasal fossa, and reaches the nasal 

 epithelium. This epithelium is, in Scomber, placed somewhat ver- 

 tically, instead of horizontally, and the olfactory nerve seems in 

 consequence to have been twisted outward, that is, upward and 

 laterally. This is indicated by a small and somewhat separate 

 bundle of fibers that crosses the dorsal surface of the nerve, 

 from within upward and laterally, during that part of its course 

 that lies outside the cranial cavity. This bundle could not be 

 traced on the intracranial part of the nerve, but it seems, neverthe- 

 less, to be the homologue of the ventro-median bundle described* 

 by me in Antia (No. 4, p. 511). No indication whatever of a 

 separate nerve, such as Pinkus describes in Protoptenis (Nos. 52 

 and 53), was found. It is however to be remembered that no 

 sections whatever were made of Scomber. 



As the olfactorius passes through the antorbital process it is 

 accompanied by three vessels, apparently veins, coming from the 

 nasal pit. One of these vessels (Fig. 61) runs backward dorsal 

 to the obliquus superior and rectus superior muscles, closely ac- 

 companying the nervus trochlearis, and at the hind end of the orbit, 

 having passed ventral to the anterior end of the trigemino-facial 

 ganglion and ventral to all the nerves that arise from that ganglion, 

 enters the trigeminal opening of the trigemino-facial chamber in the 

 petrosal. Traversing that chamber it issues at its posterior or 



