108 Trans. Acad. Sci. of St. Louis. 



ence letters will be found in figs. 4, 6 and 8. My results in 

 the main agree with Herrick's ('94). 



The olfactory nerve, consisting at its origin of two parts 

 as described by Locy, ('99) Coghill ('02) and others, runs 

 through the olfactory foramen and divides into four large 

 branches. One of these passes ventro-laterad among the 

 tubules of Jacobson's gland; a second goes dorso-laterad, a 

 third ventrad, the fourth caudad. They were not followed to 

 their ends. 



The Ramus frontalis V (F. ) runs forward above the Lamina 

 cribrosa and then upon the laterally turned edge of the medial 

 nasal process. A twig communicates with a branch of the 

 third division of the ophthalmic (C. F.). 



The Ramus maxillaris V (Max.) breaks up into twigs 

 laterad of Jacobson's organ and among the external nasal 

 glands in this region. Its relation to the maxillary bone has 

 been mentioned by Herrick. 



The first of the three main branches into which the Ramus 

 ophthalmicus trigemini divides at the fore part of the orbit 

 (Oph. Vj.) turns around the caudal end of the nasal sac 

 in the wide interval between the antorbital process and the 

 Lamina cribrosa. In older animals this nerve enters the nasal 

 capsule by the orbito-nasal foramen in the posterior cupola. 

 Further forward it passes under the tip of the Lamina and 

 then runs close to the side of Jacobson's organ. 



The second main branch of the ophthalmic (Oph. Vj) en- 

 ters the space between the nasal sac and th6 Crista trabeculae 

 and turning ventrad passes over the antorbital process to 

 anastomose with the Ramus palatinus of the VII (P). 



The third main branch of the trigeminal in the orbit (Oph. 

 Vg) enters the nasal capsule beneath the caudal margin of the 

 Lamina cribrosa close to the cranial side wall. It passes for- 

 ward dorsal to the olfactory nerve and comes out of the nasal 

 capsule at the medial incisure (later a foramen). The com- 

 municating branch to the Ramus frontalis (C. F.) and the 

 branch accompanying the nasolacrimal duct (R. nl.) run 

 under the Lamina cribrosa and emerge through slight notches 

 in its cephalic edge. 



