108 ELEMENTARY BIOLOGY. [CHAP. 



spinal nerve. Best seen on turning the aorta to 

 one side. 



d. The rami communicantes ; relatively long com- 

 missures between c and the trunks of the spinal 

 nerves. 



e. The distribution of the sympathetic ; best studied 

 in the pelvic region, and rendered the more 

 conspicuous if a little acetic acid be added to 

 the water. Vaso-motor nerves ; arising from the 

 ganglia and passing to the aorta. Viscero-motor 

 nerves ; seen to arise from both sympathetic and 

 lumbo-sacral plexus for distribution to the pelvic 

 viscera. 



f. The cranial sympathetic. Remove the aortic arches 

 with care and follow the sympathetic forwards, 

 dissecting as at § 4. ii. With a little care the above 

 can be traced to the Gasserian ganglion ; passing 

 internally to the auditory capsule and entering 

 into connection, en route, with the post-auditory 

 nerves. 



6. The further course of the facial and vagus nerves 

 (7th and 10th cranial). 



Pin a frog down upon its side and remove the 

 integument of the head, together with the arm and 

 shoulder-girdle and body-wall adjacent. Pull down 

 the stomach and pin it back, so as to put the me- 

 sentery on the stretch and fully to expose the near 

 lung and the heart. 



a. Note the course of the mandibular nerve (§ 4. 

 d. /?). It will .be seen to run backwards and 

 downwards immediately in front of the squamosal 



