310 



VASO-MOTOR FIBRES OF THE EAR. [BOOK i. 



Au 



VM.C 



ments of division and stimulation in a series of animals, we may 

 trace the path of these impulses from the lower cervical ganglion, 

 Fig. 58, through the annulus of Vieussens to 

 the ganglion stellatum or first thoracic gang- 

 lion, and thence either along the ramus com- 

 municans (visceral branch) to the anterior 

 root of the second dorsal nerve, and thus to 

 the spinal cord, or lower down along the 

 thoracic sympathetic chain, and thence by 

 other rami comrnunicantes to some other of 

 the upper dorsal nerves, and thus to the 

 spinal cord. The path taken by these vaso- 

 motor impulses for the ear is in fact very 

 similar to that of the augmentor fibres for 

 the heart (cf. Fig. 57) from the spinal cord 

 up to the annulus of Vieussens and to the 

 lower cervical ganglion ; but there they part 

 company. We can thus trace these impulses 

 along the cervical sympathetic to the anterior 

 roots of certain dorsal nerves, and through 

 these to a particular part of the spinal cord, 

 where we will for the present leave them. 

 We may accordingly speak of vaso-motor 

 fibres for the ear as passing from the dorsal 

 spinal cord to the ear along the track just 

 marked out ; stimulation of these fibres at 

 their origin in the spinal cord or at any 



FIG. 58. DIAGRAM ILLUSTRATING THE PATHS OF VASO-CONSTRICTOR FIBRES ALONG 

 THE CERVICAL SYMPATHETIC AND (PART OF) THE ABDOMINAL SPLANCHNIC. 



Aur. artery of ear. G.C.S. superior cervical ganglion. AM. SpL upper roots 

 of and part of abdominal splanchnic nerve. V.M.C. vaso-motor centre in medulla. 

 The other references are the same as in Fig. 57, 160. The paths of the constrictor 

 fibres are shewn by the arrows. The dotted line in the spinal cord, Sp.C., is to 

 indicate the passage of constrictor impulses down the cord from the vaso-motor 

 centre in the medulla. 



part of their course (along the anterior roots of the second, 

 third or other upper dorsal nerves, visceral branches of those 

 nerves, ganglion stellatum or upper part of thoracic sympathetic 

 chain, annulus of Vieussens, &c. &c.) leads to constriction in the 

 blood vessels of the ear of that side ; and section of these fibres 

 at any part of the same course tends to abolish any previously 

 existing tonic constriction of the blood vessels of the ear, though 

 this effect is not so constant or striking as that of stimulation. 



167. We must now turn to another case. In dealing with 

 digestion we shall have to study the sub-maxillary salivary gland. 

 We may for the present simply say that this is a glandular mass 

 well supplied with blood vessels, and possessing a double nervous 

 supply. On the one hand it receives fibres from the cervical 



