88 



THE NERVOUS SYSTEM OF THE FROG. 



To see the course and distribution of the olfactory nerve, dissect 

 from the dorsal surface, removing the roof of the anterior part of 

 the skull, including the nasal bone. 



2. The optic nerve, the nerve of sight, arises from the side 



of the brain just below the optic lobe, partially crosses 

 over at the optic chiasma on the under surface of the 

 brain, and then runs outwards to the eyeball. 

 The course of the optic nerve has been fully seen in previous 

 dissections. 



3, The motor oculi is a small nerve arising from the ventral 



surface of the brain close to the median line and between 

 the crura cerebri. It supplies four of the muscles 



XI ^ 



1 e 1 .-^^^tX. Vila 



3 m 



Fig. 17. The trigeminal, facial glossopharyngeal, and pneumogastric 

 nerves of the frog, dissected from the right side. 



a, stomach : e. Eustachian tube : A, hypoglossal nerve : i, lung : 

 m, second spinal nerve : s, sinus venosus : t, squamosal : t.a, truncus 

 arteriosus : u, right auricle : v, ventricle : v.c, right anterior vena cava : 

 Va, ophthalmic branch of trigeminal : Vb, maxillary branch of trigemi- 

 nal : V c, mandibular branch of trigeminal : Vila, ]ialatine branch of 

 facial : Vllb, hyoidean branch of facial : IX, glossoi^haryngeal : 

 Xa, laryngeal branch of pneumogastric : Xb, pidmonary branch of 

 pneumogastric : Xc, cardiac branch of pneumogastric : Xd, gastric 

 branch of i)neumogastric : 2, transverse i3rocess of second vertebra : 

 3, transverse process of third vertebra. 



