VASOMOTOR SUPPLY OF THE ORGANS. 561 



providing a greater flow to the central organ at the time that it is 

 in activity must still be admitted. A general irrigation, so to speak, 

 is provided for by this means. Local vasomotors may be used to 

 divert this flow mainly through one or another cerebral area. 



Vasomotor Nerves of the Head Region. The vasomotor 

 supply of the various parts of the head, including the mouth cavity, 

 has been investigated by many observers. It would appear from 

 the results of most of these investigations that the vasoconstrictor 

 supply for the skin, including the ears, the eye, the mouth, and 

 buccal glands, is derived mainly, if not entirely, from the sympa- 

 thetic nervous system. These fibers arise from the spinal cord in the 

 upper thoracic nerves, first to the fifth or sixth, emerge by the rami 

 communicantes to the sympathetic chain, in which they pass upward 

 and end, for the most part, in the superior cervical ganglion. From 

 this ganglion they are distributed, by various routes, as postgan- 

 glionic fibers. In one interesting instance at least the constrictor 

 'fibers for the head take a somewhat different course. It was 

 shown by Schiff, long ago, that in the rabbit the ear receives vaso- 

 motor fibers from the auricularis magnus nerve, a branch of the 

 third cervical nerve. Later investigations indicate (Meltzer) that 

 the ear, in fact, receives most of its vasoconstrictor fibers by this 

 route. Fletcher, however, has shown that these fibers do not emerge 

 from the brain in the roots of the third cervical, but rather in the 

 general outflow from the thoracic region. After reaching the sym- 

 pathetic chain these particular fibers pass to the third cervical by 

 the gray rami from the first thoracic ganglion, which communicate 

 with a number of the cervical nerves. On the other hand, the vaso- 

 dilator fibers for the head are supplied in part by way of the cervical 

 sympathetic, following the same general path as the constrictors, 

 and in part by way of the cranial nerves (seventh, ninth) and 

 the sympathetic ganglia with which they connect. According to 

 Langley, the outflow of the seventh nerve passes to the spheno- 

 palatine ganglion, whence as postganglionic fibers they accompany 

 the branches of the superior maxillary nerve and cause vasodila- 

 tation in the membrane of the nose, soft palate, tonsils, uvula, roof 

 of mouth, upper lips, gums, and pharynx. The fibers that emerge 

 in the ninth pass in part directly to the tongue and in part terminate 

 first in the otic ganglion, whence they are distributed with the 

 branches of the inferior maxillary to the lower lips, cheeks, gums, 

 parotid and orbital glands. Dastre and Morat describe the vaso- 

 dilators in the cervical sympathetic as reaching the fifth cranial 

 nerve by communicating branches from the superior cervical 

 ganglion and state that they cause dilatation of the bucco-facial 

 region, that is, the lips, the gums, cheeks, palate, nasal mucous 

 membrane, and the corresponding skin areas. 

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