WORK UPON VISCERAL AND ALLIED NERVES. 41 



The pre-ganglionic vaso-motor nerves to the tail ^ leave 

 the cord by the third and fourth lumbar nerves and to a 

 less extent by the second lumbar. By nicotine it is shown 

 that these fibres are connected with cells in the coccygeal 

 ganglia. 



To the Head. — The pre-ganglionic fibres constricting 

 the vessels of the head,^ in the cat and dog, leave in the 

 first to fifth thoracic anterior roots inclusive, but chiefly in 

 the second, third and fourth. They terminate in cells in 

 the superior cervical ganglion.^ Certain fibres causing 

 dilatation of the vessels in the gums and lips in the dog, 

 have also been shown by Langley and Dickinson to be 

 connected with cells in the superior cervical ganglion.^ 



To the Brain. — Roy and Sherrington,^ in a paper dealing 

 with the general physics of the circulation in the brain, were 

 unable to gain any satisfactory evidence of vaso-motor 

 fibres to the cerebral vessels in the nerves of the neck, 

 "and that therefore there is no evidence of their existence 

 outside the cerebro-spinal canal". Bayliss and Hill*^ have 

 also carried out many experiments with the aim of deter- 

 mining the presence of these vaso-motor fibres, but again 

 with neorative results. 



The course of efferent fibres from the cord is almost 

 universally considered as through the anterior roots, and so 

 general is this that any statement of the presence of efferent 

 fibres in the posterior roots should be most critically ex- 

 amined. In 1876 Strieker '^ described his experiments and 

 results upon the vascular nerves in the sciatic. His method 

 was by thermometric observation of the foot after section 

 or stimulation of the nerves in differ'ent parts of their course. 

 He describes the posterior roots of the fourth and fifth lum- 

 bar nerves of the dog as always containing vaso-dilator 



^ Langley, loc. cit., p. 311. 



2 Langley, Phil. Trans.., vol. clxxxiii., p. 85, 1892. 



■^ Langley and Dickinson, Proc. Roy. Soc, vol. xlvii., p. 379, 1889-90. 



* See also l^^n^ey, Journ. of Physiol., vol. ii., p. 146, 1890. 



^ Journ. of Physiol., vol. xi., p. 85, 1890. 



6 Ibid., vol. xviii., p. 334, 1895. 



''' Sitz. d. k. Ak. d. IViss. IVien, vol. Ixxiv., iii., p. 173, 1876. 



