THE S YMPA THETIC NER VE-FIBRES. 483 



gland was suggested before Ludwig's discovery of secretory nerves, and was 

 definitely stated by Schiff in 1851. 



The course of the nerve-fibres to the parotid gland was also investigated by 

 Bernard. He obtained secretion in the dog by stimulating the auriculo- 

 temporal branch of the fifth nerve, and a cessation of reflex secretion by ex- 

 tirpation of the otic ganglion. He considered that the secretory fibres came 

 from the small superficial petrosal nerve, and that the superficial petrosals 

 and the chorda tympani arose from the nervus intermedius of Wrisberg. 

 Abolition of the reflex secretion in the rabbit was observed by Schiff on simple 

 section of the small superficial petrosal. Loeb found that section of the 

 tympanic branch of the glosso-pharyngeal nerve (i.e. of Jacobson's nerve), or of 

 the roots of this nerve in the skull, also abolished the reflex secretion, so that 

 the secretory fibres of the small superficial petrosal come from the ninth and 

 not from the facial. And Heidenhain obtained copious secretion on stimulat- 

 ing Jacobson's nerve. 



If the secretory fibres of the parotid really arise from the ninth nerve, the 

 majority of the early observations form a singular record of inadequate experi- 

 ments and hasty deductions. 



The sympathetic nerve-fibres and the nerve-cells with which 

 they are connected. -All the salivary glands receive nerve-fibres from 

 the cervical sympathetic. The fibres run from the middle or from the 

 lower part of the superior cervical ganglion to the external carotid 

 artery, and accompany its branches. On the arteries they form a plexus 

 having two main longitudinal strands. The nerve-plexus, though chiefly 

 of noii-medullated fibres, contains some medullated fibres. In the artery 

 to the submaxillary gland of the dog, there are twenty to thirty 

 medullated fibres, a few of these being 5 ,0. to 7 // in diameter, the rest 

 2 (L to 3*5 p\ the fibres run past the submaxillary ganglion in the hilus, 

 without being, so far as can be seen, connected with it. 



The sympathetic fibres both secretory and vasomotor, for the sub- 

 maxillary gland of the dog and cat, arise chiefly from the second thoracic 

 nerve, to a less extent from the third, fourth, and to a slight and vary- 

 ing extent from the 'first and fifth thoracic nerves. 1 



Langendorff 2 found that four months after hemisection of the 

 spinal cord in the upper cervical region, the cervical sympathetic pre- 

 sented its normal appearance. We may conclude, then, that the 

 glandular nerve-fibres do not descend from a secretory centre in the 

 medulla, and simply make their exit by the upper thoracic nerve roots. 



And there are several grounds for believing that the efferent sym- 

 pathetic nerve-fibres issuing from a particular nerve root are the axis- 

 cylinder processes of nerve-cells situated in the corresponding segment 

 of the spinal cord. 



pathol. dti systeme nerveux," 1858, tome ii. ; Schiff, "Lehrbuch. d. Mtiskel. u. Nerven- 

 physiologie, " 1858-1859, S. 393; Czermak, Sitzungsb. d. k. Akad. d. Wissensch.,Wien, 

 1860, Bd. xxxix. S. 526 ; Beitr. z. Anat. u. PhysioL (EcTchard), Giessen, 1860, Bd. ii. S. 

 214 ; 1863, Bd. iii. S. 49 ; Navrocki, Stud. d. physiol. Inst. zu Breslau, Leipzig, 1865, 

 Heft 4, S. 123 ; Loeb, Beitr. z, Anat. u. Physiol. (Hckhard), Giessen, 1869, Bd. v. S. 1 ; 

 Heidenhain, Arch. f. d. ges. PhysioL, Bonn, 1878, Bd. xvii. S. 15; Bernard, "Lecons de 

 physiol. operatoire," 1879. 



1 Langley, Phil. Trans., London, 1892, vol. clxxxiii. p. 104. 



-Arch. f. d. ges. Physiol., Bonn, 1894, Bd. Iviii. S. 165. Strictly speaking, the 

 experiment only shows that the great majority of the nerve fibres of the cervical 

 sympathetic have their trophic centre in the spinal cord below the hemisection. If even 

 a considerable number of fibres had degenerated, they would have been absorbed in the 

 time allowed, and would have left no recognisable trace. 



