THE SUPRA-ORBITAL TRUNK. I95 



IX. — The Truncus Supra-Orbitalis. 



The supra-orbital trunk contains lateralis fibres from 

 the dorsal lateral line ganglion, general cutaneous fibres 

 from the Gasserian ganglion and a smaller number of 

 communis fibres from the geniculate ganglion. The first 

 comprise the r. ophthalmicus superficialis VII; the 

 second the r. ophthalmicus superficialis V; the third in 

 other fishes are usually relegated to the r. ophthalmicus 

 superficialis V, as in Amia. The two fine-fibred compo- 

 nents are so closely united that it is impossible to separate 

 them far beyond the tip of the Gasserian ganglion (com- 

 pare the cross-sections, Figs. 22 to 25). But the coarse- 

 fibred lateralis component can be easily followed micro- 

 scopically throughout the entire extent of the trunk. 

 The trunk runs dorsad and cephalad along the outer face 

 of the cranial wall under the post-orbital process and carries 

 with it for a considerable distance an extension of the 

 Gasserian ganglion. 



Near the cephalic border of the post-orbital process, 

 but before the tip of the ganglion has been reached, a 

 fine-fibred branch separates dorsally (Fig. 4, so, i). It 

 seems to include both general cutaneous and communis 

 fibres. It passes through a foramen in the sphenotic bone 

 into the cranial cavity and then runs dorsad in the 

 meninges. The subsequent course is closely parallel with 

 that of the most cephalic twig of the third root of the r. 

 lateralis accessorius, with which, however, it does not 

 anastomose. It passes through a foramen in the frontal 

 bone and then divides into two twigs which apparently 

 distribute to the skin overlying the supra-orbital canal. 



Slightly farther forward, i. e., just at the tip of the 

 ganglion, another fine-fibered branch separates dorsally 

 {so. 2). It sends one twig laterally along the cephalic 



