ADVANCED EXPERIMENTAL PHYSIOLOGY 



157 



this is the largest; (Dep) the depressor, a fine nerve which may 

 be traced up to where it arises by two branches, from the 

 superior laryngeal nerve and from the vagus ; (Sy) the cervical 

 sympathetic, a slender thread, which may be traced up to the 

 superior cervical sympathetic ganglion. In the cat vagus and sym- 

 pathetic are one, and the depressor is separate on the left side only as 



Dig 



MJv. 



FIG. 158.- Dissection of the vagus, the depressor, and cervical sympathetic nerves 

 in the rabbit. (Li von.) 



a rule. Tie threads round these nerves, ready for their excitation. 

 Pass two ligatures under the carotid, and tie the upper one. Put a 

 clip on the artery below. Make a V-shaped incision, and insert and tie 

 in the cannula. Connect the cannula with the mercury manometer by 

 pressure tubing, and with the glass syringe fill the tube and cannula 

 with a sat. sol. of Na. 7 S0 4 . Close the side tube of the cannula with a 

 piece of rubber tube, in which a solid glass rod is inserted. Carefully 

 raise the pressure in the manometer by means of the syringe to about 

 100 mm. Hg, and clip off the syringe. Open the clip on the artery, 

 and record the blood pressure on the slow drum. Faradise the 

 peripheral end of the vagus and observe the inhibition. Stop the 

 artificial respiration for a short time, and observe the effect of asphyxia. 



