SfGJVS OF FIBRES OF CERVICAL SYMPATHETIC, 619 



of the " nerf intercostal " (frhe cervical sympathetic). As the result of section of 

 the latter nerve, he found decrease in the size of the pupil, projection of the 

 " membrane particuliere du grand coin de Toil " (the nictitating membrane), 

 reddening of the conjunctiva, an increase in the fluid bathing the eye, and a 

 decrease in the convexity of the cornea. 



Biffi, 1 in 1846, noticed that stimulation of the cervical sympathetic caused 

 dilatation of the pupil. 



Bernard, 2 in 1852, observed that section of the cervical sympathetic led to 

 the dilatation of the vessels of the ear, and increase of temperature of the skin 

 of the head on the side of the cut nerve. This was soon followed by observa- 

 tions of the effect of stimulating the cervical sympathetic. Bernard/ 5 Brown- 

 Sequard, 4 and Waller 5 all found contraction of the blood vessels of the ear, and 

 decrease of temperature. The two latter observers attributed the contraction of 

 the vessels to the stimulation of vasomotor fibres, and the temperature changes 

 to variations in the amount of blood ; whilst Bernard was inclined to attri- 

 bute the variations in temperature, in part at least, to special calorific and 

 frigorific nerves. 



Tonic action ; effect of section of cervical sympathetic. The 

 sympathetic nervous system exercises a tonic action on certain of the 

 structures to which it runs, but not on all of them. In the cervical 

 sympathetic, the vaso-constrictor fibres, the pupillo-dilator fibres, and 

 the constrictor fibres to the unstriated muscle of the eye, are in a state 

 of constant action, only broken by occasional inhibition occurring in 

 the central nervous system ; whilst the secretory fibres, the pilo-motor 

 fibres in the cat, 6 and the vaso-dilator fibres to the bucco-facial region 

 of the dog, are normally at rest, broken only by an occasional excita- 

 tion. Section of the cervical sympathetic will, then, only cause paralytic 

 effects in those tissues which are in a state of tonic contraction. It 

 causes a dilatation of the blood vessels, and an accompanying rise of 

 temperature in the ear and the skin of the head. The vascular effects 

 in other parts are less pronounced ; they are generally marked in the 

 conjunctiva, but slight or absent in the mucous membrane of the 

 mouth. The hypersemia of the lachrymal and salivary glands leads to 

 a greater secretion than normal, whenever secretion is in any way set 

 up. And, similarly, the hypersemia of the nasal mucous membrane may 

 lead to frequent sneezing. Section of the cervical sympathetic causes 

 also a considerable narrowing of the palpebral aperture and projection of 

 the nictitating membrane, and some retraction of the globe of the eye. 



The duration of the several paralytic effects we shall consider 

 later (p. 655). 



Origin of fibres of the cervical sympathetic. The origin of the 

 fibres of the cervical sympathetic from the spinal cord, by which is 

 meant the spinal nerves which convey fibres from the spinal cord to the 

 sympathetic, can be determined by stimulating the several spinal nerves 

 in the vertebral canal, after removal of the corresponding portion of the 

 spinal cord, and observing which of them cause the effects also caused 

 by stimulating the cervical sympathetic. The effects being noted, the 



1 Serafino Biffi, "Milanese Inaug. Diss.," Pavia, 1846. (Quoted.) 



2 Compt. rend. Acad. d. sc., Paris, 1852, tome xxxiv. p. 472. 



3 Compt. rend. Soc. de biol., Paris, October and November 1852. 



4 Phila. Med. Exam., 1853. 



3 Compt. rend. Acad. d. sc., Paris, 1853, tome xxxvi. p. 378. 



8 In the ape, after section of the cervical sympathetic, the hairs of the head on the out- 

 side are somewhat less erect than on the intact side (Sherrington). 



