24 GUIDES FOR VERTEBRATE DISSECTION 



already mentioned. Trace it outwards and backwards to its 

 union with Jacob son's commissure. 



The next branch is the common maxillo-mandibularis trunk 

 of the trigeminal nerve (V). Trace it laterally to its division into 

 maxillaris and mandibular nerves. The next anterior is the 

 superficial temporal branch of the trigeminal nerve, the distal 

 portion of which has probably been removed with the muscles. 

 It supplies the adjacent region of the top of the head. 



Now carefully remove the tissues between the eye and the 

 cranium, keeping watch for the ophthalmic branch of the fifth 

 nerve, which runs forward from the common prootic ganglion, 

 parallel to the side of the cranium. Trace it forward to the tip 

 of the snout. 



The ophthalmic nerve crosses the optic nerve (II), which runs 

 obliquely forwards and outwards from beneath the diencephalon 

 to the eyeball. 



Running parallel to the ophthalmic nerve in the orbital region, but 

 passing beneath the optic nerve, is a part of the oculomotor nerve (III). 

 The branches of this, as well as the whole of the trochlearis (IV) and 

 abducens (VI) nerves, are difficult to trace. 



The olfactory nerve (I) should be traced forward from the 

 rhinencephalon to its distribution to the olfactory organ. 



Add these nerves to the sketch of the brain. 



Turn the head on the side and follow the branches of the 

 vagus, hyomandibular, glossopharyngeal, maxillaris, and man- 

 dibular nerves outwards and downwards, and trace all but the 

 maxillaris on to the lower jaw. 



Now remove the lower jaw; remove the skin from the roof 

 of the mouth, taking great care not to take the underlying nerves 

 with it. Several nerves will be exposed. Of these note especially 

 the palatine nerve, a branch of the seventh, which passes nearly 

 straight forward near the middle line across the inner side of the 

 floor of the orbit. Trace its branches as far as convenient and 

 also follow it dorsally to its origin from the common prootic 

 ganglion. 



Add all these nerves to your drawing. 



Cut through the olfactory and optic nerves, and with the 

 forceps grasping the olfactory, carefully lift up the brain, cutting 

 the successive nerves as close to the cranial wall as is possible. 



