THE NERVOUS SYSTEM 141 



pass ventral to the M. obliquus superior, and dorsal to the M. obli- 

 quus inferior. 



(iv) Mesial branch (V^'', Hoffmann). The mesial terminal branch 

 (n.5a.M.) passes through the Foramen orbito-nasale mediale in the 

 antorbital cartilage slightly dorsal to the origin of the M. obliquus 

 superior. On entering the nasal capsule the nerve turns mesially and 

 then anteriorly, passing over the nasal sac dorsal to the olfactory 

 nerve. At a point a little posterior to the level of the external nares 

 it breaks up into several fine terminal twigs which penetrate foramina 

 in the premaxilla and the nasal bone, and supply the skin of the snout. 



Just before this branch enters the For. orbito-nasale mediale, 

 while it is still within the orbit, it gives a small lateral branch which 

 fuses with a twig from the lateral terminal branch and then enters 

 the nasal capsule separately from the main nerve. It passes dorsal to 

 the nasal sac, and turns first mesially, then sharply laterally, and 

 finally perforates the nasal capsule laterally to suppy the skin near 

 the ductus naso-lacrimalis. 



The branch just described is composed of fibres from both lateral 

 and mesial terminal branches in varying proportions, and although 

 its course is somewhat peculiar its presence seems to be reasonably 

 constant. 



(v) Lateral branch (V^"^', Hoffmann). The lateral terminal branch 

 (n.5a.L.) gives off" one or two small twigs within the orbit which turn 

 sharply lateralwards, and supply the skin over the upper jaw near the 

 anterior angle of the orbit. The main nerve then itself turns lateral- 

 wards, penetrates the For. orbito-nasale laterale, and enters the pos- 

 tero-lateral corner of the nasal capsule. It crosses the corner of the 

 capsule obliquely, more or less lateral to the olfactory epithelium, 

 and passes through the fenestra infraconchalis and then through 

 foramina in the maxilla to supply the skin of the face laterally of the 

 nasal capsule. 



(y\) Ventral branch(y'^^\¥Lo&m2inn). The ventral terminal branch 

 (n.5a.V.) enters the nasal capsule by the For. orbito-nasale mediale 

 directly between the origins of the superior and inferior oblique 

 muscles, a little ventral to the mesial terminal branch, and close to 

 the floor of the capsule. After passing through the foramen the 

 nerve remains entirely ventral to the olfactory epithelium and, turn- 

 ing slightly mesially, anastomoses with the R. palatinus VII just 

 mesial to the internal narial opening. In sections ganglionic cells are 

 discernible at the point where these two nerves join, and even in dis- 

 sections a swelling suggestive of a ganglion is noticeable. The nerves 

 resulting from this fusion are of course mixed, and contain both 



