INNERVATION OF THE BLOOD-VESSELS OF DIFFERENT ORGANS 423 



One of the most striking vasomotor reactions obtainable with the 

 aid of this nerve is the following: If the blood-vessels in the ear of a 

 rabbit are rendered more clearly perceptible by transillumination, it 

 can readily be observed that the division of this nerve occasions a very 

 decided vascular relaxation. Many blood-vessels which were previ- 

 ously quite invisible to the naked eye, are now sharply outlined, and 

 the ear on the operated side is distinctly warmer than the one on the 

 normal side. If the distal (cephalic) end of this nerve is stimulated, a 

 vasoconstriction soon results which betrays itself most unmistakably 

 by a diminution in the caliber of the central artery and its principal 

 branches. These vessels grow smaller and smaller until they can 



FIG. 223. THE VASOMOTOR REACTIONS IN THE EAR OF THE RABBIT ON DIVISION 



AND STIMULATION OF THE CERVICAL SYMPATHETIC NERVE. 



A. Normal. B. After division of the cervical sympathetic nerve. C. On stimu- 

 lation of the distal end of the divided cervical sympathetic nerve. 



scarcely be made out. The veins remain visible for a much longer 

 time, but eventually collapse owing to the cessation of the arterial 

 influx. This ear now feels distinctly colder than the one on the normal 

 side. On discontinuing the stimulation, the arteries again relax until 

 they have attained their former caliber. These changes may be pro- 

 duced again and again, but naturally, only at intervals, to avoid fatigu- 

 ing this vasomotor mechanism. 



The superior cervical ganglion also serves as the distributing center 

 of the sympathetic fibers to the sublingual and submaxillary glands. 

 These fibers follow in the course of the art. glandularis submaxillaris. 

 The aforesaid organs also receive a second nerve supply which is de- 

 rived from the bulbar autonomic system and appears peripherally in 

 the form of a small nerve known as the chorda tympani. The latter 

 leaves the system of the facial nerve and attaches itself at first to the 

 lingual nerve of the fifth system. When it reaches the region of Whar- 



