596 APPENDIX 



The nerve can be traced to where it passes through a hole in the 

 pelvic bone. Thrust a seeker through this hole and then cut away 

 the tissues on the front surface of the pelvis until the seeker is 

 exposed. The nerve will thus be brought into view, and can be 

 traced for a short distance to the point where it emerges from the 

 spinal canal. 



Returning to the nerve on the outer surface of the thigh follow 

 it downward, noting that it gives off occasional branches to contigu- 

 ous muscles. A short distance behind the knee the nerve divides 

 into two branches. One of these, the peroneus, passes across the 

 gastrocnemius muscle on its outer surface, then plunges beneath 

 it and passes down the shank close to the fibula. It can be followed 

 by cutting away the overlying tissue. The second branch of the 

 sciatic, the tibialis, passes directly into the muscular mass of the 

 calf, then turns downward toward the foot. Follow it as far as 

 possible, cutting away overlying tissues carefully. 



A Typical Cranial Nerve: The Vagus. Make an incision along 

 the mid-line of the under surface of the body its entire length. 

 Separate the muscles of the neck until the trachea (wind-pipe) is 

 exposed in the mid-line. Follow around the left side of the trachea, 

 separating the muscles, but not cutting them, until a sheath of 

 connective tissue inclosing blood-vessels and nerves is found. This 

 sheath is usually in close contact with the side of the trachea. 

 With a blunt instrument open the sheath and separate the nerves 

 from the adjacent artery for the space of an inch or more. Careful 

 observation discloses two nerves in close contact with each other. 

 The larger is the vagus. Follow it toward the head. At the level of 

 the larynx (vocal apparatus) it gives off a branch, the superior 

 laryngeal. Continue the dissection forward to the point where the 

 nerve enters the skull. An enlargement, the ganglion nodosum, is 

 seen just here. 



Return to the point where the vagus was first separated, and 

 carry the dissection backward. Separate overlying tissues, but do 

 not cut through them except when absolutely necessary for prog- 

 ress. At the junction of neck with thorax there are some large 

 veins which may bleed. If any such are cut accidentally the blood 

 should be carefully wiped away with cotton to keep the field of 

 dissection clear. Follow the nerve into the thorax to the level of the 

 root of the lung, A short distance above this point a branch of 



