496 AN AMERICAN TEXT-BOOK OF PHYSIOLOGY. 



Vaso-motor Nerves of Head. The cervical sympathetic contains vasocon- 

 strictor fibres for the corresponding side of the face, the eye, ear, salivary 

 glands 1 and tongue, and possibly the brain. The spinal vaso-constrictor 

 fibres for the vessels of the head in the cat and dog leave the cord in the 

 first five thoracic nerves ; 2 in the rabbit, in the second to eighth thoracic, seven 

 in all. 3 



Vaso-dilator fibres for the face and mouth have been found in the cervical 

 sympathetic by Dastre and Morat, 4 leaving the cord in the second to fifth 

 dorsal nerves, and uniting (at least for the most part) with the trigeminus by 

 passing, according to Morat, 5 from the superior cervical sympathetic ganglion 

 to the ganglion of Gasser. Other dilator fibres for the skin and mucous 

 membrane of the face and mouth arise apparently in the trigeminus, for the 

 stimulation of this nerve between the brain and Gasser's ganglion causes dila- 

 tation of the vessels of the face, 6 and in the nerve of Wrisberg. 7 



The vaso-motor nerves of the tongue have been recently studied by Isergin. 8 

 The lingual and the glosso-pharyngeal nerves are recognized by all authors as 

 dilators of the lingual vessels. The sympathetic and the hypoglossus contain 

 constrictor fibres for the tongue. It is possible that the lingual contains also 

 a small number of constrictor fibres. Most if not all these vaso-motor fibres 

 arise in the sympathetic and reach the above-mentioned nerves by way of the 

 superior cervical ganglion. 9 They degenerate in from three to five weeks after 

 the extirpation of the ganglion. 



Morat and Doyon 10 cut the cervical sympathetic in a curarized rabbit and 

 examined the retinal arteries with the ophthalmoscope. They were found 

 dilated. The excitation of the cervical sympathetic caused constriction, the 

 excitation of the thoracic sympathetic dilatation of these vessels. The retinal 

 fibres leave the sympathetic at the superior cervical ganglion and pass along 

 the communicating ramus to the ganglion of Gasser, whence they reach the 

 eye through the ophthalmic branch of the fifth nerve, the gray root of the 

 ophthalmic ganglion, and the ciliary nerves. Most, or all, of the fibres for 

 the anterior part of the eye are found in the fifth nerve. 



Lungs. The methods ordinarily employed for the demonstration of vaso- 

 motor nerves cannot without danger be used in the study of the innervation 



1 Compare Vulpian, 1885, p. 853. 2 Langley, 1892, p. 102. 



3 Langley, 1892, p. 104. 



4 Dastre and Morat, 1884, pp. 116, 129; see also Pye-Smith, 1887, p. 25; Langley, 1890, p. 

 146; Langley and Dickinson, 1890, p. 380; Morat, 1891, p. 87; Piotrowski, 1892, p. 464; 

 Langley, 1892, p. 97. 



5 Morat, 1889, p. 201. 



6 Vulpian, 1885, p. 982; compare Dastre and Morat, 1884, p. 118; Langley, 1893,iv.; Pio- 

 trowski, 1894, p. 278. 



7 Vulpian, 1885, p. 1038. 



8 Isergin, 1894, p. 441 ; other literature : Anrep and Cybulski, 1884; Vulpian, 1885, pp. 854, 

 1038 ; Piotrowski, 1887, p. 454 ; 1894, p. 246. 



9 For evidence that probably all vaso-constrictor fibres to the head (nerve-cells of the second 

 class) end in the superior cervical ganglion, see Langley and Dickinson, 1889, p. 425. 



10 Morat and Doyon, 1892, p. 60 ; see also Langley, 1893, iv. ; Doyon, 1890, p. 774 ; 1891, p. 154. 



