PRy4CTlC/IL DIRECTIONS. 467 



the branch of this nerve which runs to the inferior oblique muscle, 

 and on it the ciliary ganglion; find the branches to the ciliary gan- 

 glion from the ophthalmic nerve and follow them (p. 371). Follow 

 also the short ciliary nerves (p. 370) to the eyeball. 



1 1. Trace the third nerve (p. 369) to its foramen of exit and find 

 its branches. Where it passes between the superior and lateral recti, 

 find the ophthalmic nerve (p, 370) by its side and trace its branches. 



12. Find the fourth nerve (p. 370), passing outside of the lateral 

 rectus at its origin and entering the superior oblique. 



13. Follow the third, fourth, fifth, and sixth nerves into the skull 

 by chipping away the bone and removing the dura. Note the semi- 

 lunar or Gasserian ganglion (p. 370, and Fig. 138, k) and the origin 

 of the fifth nerves from it, and the relation of the ventral root of the 

 fifth nerve to the mandibular nerve. 



2. Spinal Nerves. 



The spinal nerves may be dissected on the same side used for 

 dissecting the cranial nerves. (If an undissected specimen is used, 

 remove the skin from the side of the neck, and cut the sternomastoid, 

 sternohyoid, and sternothyroid muscles, as directed for the vagus and 

 sympathetic.) 



Cervical A^erves (p. 383). — The ventral rami of the cervical nerves 

 are to be sought as they pass out between the bundles of the 

 scalenus, or between the scalenus and longus capitis, in the neck. 

 This region has already been uncovered in dissecting the vagus and 

 sympathetic (Fig. 156). Dissect first the second cervical (p. 385). 

 Find its ventral ramus as it emerges between the levator scapulae 

 ventralis and cleidomastoid (Fig. 158, 2), and follow its branches, — 

 the auricularis magnus (5) and cutaneus colli (6). Find its dorsal 

 ramus, the great occipital nerve (p. 384), by reflecting the clavo- 

 trapezius muscle; the nerve will be found emerging from the under- 

 lying muscles close to the craniomedial angle of the clavotrapezius, 

 near its origin. Trace the nerve in both directions. 



The ventral ramus of the first cervical (p. 385) will be found 

 emerging from beneath the wing of the atlas, a little distance craniad of 

 the second (Fig. 156,7"). Trace it. To find its short dorsal ramus, 

 the suboccipital nerve (p. 384), it is necessary to dissect apart the 

 muscles on the dorsal side of the atlas till the nerve is found passing 

 from the atlantal foramen. 



Dissect the third, fourth, and fifth nerves (p. 385, and Fig. 158). 



Brachial Plexus (p. 386, and Figs. 159 and 160). — The brachial 

 plexus has been partly uncovered in dissecting the vagus and sympa- 

 thetic. (If a new specimen or the opposite side is used, reflect the 

 skin from the ventral surface of the thorax and arm, and cut the 

 pectoral muscles, thus uncovering the vessels and nerves of the 

 axilla. ) Reflect the skin from the ventral surface of the upper arm. 

 (Do not use scalpel, but tear the skin from the muscles. In this- 



