PRACTICAL DIRECTIONS. 469 



397) by removing the integument from the medial side of the leg 

 (see Fig. 127, p. 310). To dissect the sacral nerves (p. 399) separate 

 the innominate bones at the pubic symphysis and divaricate them. 

 Find the nerves arising from the sacral plexus, by cutting the levator 

 ani muscle. After N. hemorrhoidalis inferior and N. pudendus have 

 been traced, the rectum and urogenital organs may be removed, tak- 

 ing great care not to remove more than is necessary. To dissect the 

 great sciatic nerve (p. 400, and Fig. 163), separate the biceps and 

 caudofemoralis near their proximal ends and find the large nerve- 

 trunk (a). Then lift the biceps away from the nerve, cut that muscle 

 near its middle, and reflect it. The nerve may now be followed to 

 its terminal branches; during the process cut the muscles only when 

 absolutely necessary. The inferior gluteal nerve (;) will be found 

 on the dorsal surface of the great sciatic; by cutting the caudofemo- 

 ralis and gluteus maximus muscles near their insertions and turning 

 them back the distribution of the nerve may be followed. The 

 superior gluteal (y) will be found at the cranial margin of the pyri- 

 formis by reflecting the gluteus medius in the same way; the tensor 

 fasciae latae may also be cut. 



SENSEORGANS. 



I. The Eye (p. 410). 



Use any specimen on which one side of the head has been left 

 intact. Remove the head from the body by cutting through the neck 

 a little craniad of the first rib. 



Study the eye externally. Observe the eyelids, the conjunc- 

 tiva, nictitating membrane with its cartilage, and the Harderian 

 gland (Fig. 165); the two openings of the lachrymal duct, the 

 Meibomian glands if possible. 



Remove the zygomatic arch and expose the orbit and the struc- 

 tures which it contains. Study the periorbita (p. 409), and find the 

 lachrymal gland (p. 410). 



Study the muscles of the eyeball (p. 411, and Fig. 166). The 

 lateral rectus on the lateral surface will perhaps be first found, and 

 its tendon traced beneath the inferior oblique. Use great care not 

 to injure the levator palpebra; superioris. 



After studying the muscles, find the optic nerve. Cut it and the 

 muscles, and remove the eyeball for farther study. 



Ilie Eyeball (p. 412, and Fig. 167). — For an examination of the 

 eye it is well to have a fresh specimen and one hardened in formalin 

 or alcohol. The hardened specimen is more essential, however. An 

 eye from one of the specimens used in dissection is usually satisfac- 

 tory. All accessory portions should be trimmed from the eyeball, 

 leaving only the spherical ball with a short stalk formed by the optic 

 nerve. 



Observe such features of the eye as can be seen externally: the 

 optic nerves, sclerotic, cornea, iris, and pupil. This should be done 



