756 THE NEKVOUS SYSTEM. 



for convenience of description be dealt with in four parts cephalic and cervical, 

 thoracic, lumbar, and pelvic. 



I. PAES CEPHALICA ET CEEVICALIS SYSTEMATIS SYMPATHICL 



The cephalic and cervical part of each sympathetic trunk is to be regarded 

 as an upward prolongation of the primitive sympathetic system along the great 

 vessels of the neck. It is characterised by the absence of segmental ganglia and by 

 the absence of white rami communicantes joining it to the spinal nerves. Its con- 

 nexion with the spinal nervous system is through the white rami communicantes 

 of the upper thoracic nerves, which join the gangliated trunk in the thorax, and 

 stream upwards into the cervical portion of the trunk. The trunk possesses two 

 or three ganglia, from which branches are distributed to structures belonging to 

 head, neck, and thorax : (1) motor fibres to involuntary muscles (e.g. dilator of the 

 pupil) ; (2) vaso-motor fibres for arteries of the head, neck, and upper limbs ; (3) 

 pilo-motor fibres (along the cervical spinal nerves) to the skin of the head and 

 neck ; (4) cardio-motor fibres ; and (5) secretory fibres (e.g., submaxillary gland). 



Each gangliated trunk in the neck is placed upon the prevertebral muscles and 

 behind the carotid vessels of the corresponding side. It extends from the root of 

 the neck, where it is continuous, in front of the neck of the first rib. with the 

 thoracic portion of the trunk, to the base of the skull, where it ends in the 

 formation of plexiform branches upon the internal carotid artery. It consists 

 of a narrow cord composed of inedullated and non-medullated fibres, with two 

 or three ganglia a superior ganglion at the upper end, an inferior ganglion at 

 the point of junction with the thoracic portion of the trunk, and a middle 

 ganglion, varying in position and often absent. 



Ganglion Cervicale Superius. The superior cervical ganglion, situated at the 

 base of the skull, lies between the internal jugular vein and the internal carotid 

 artery. It is the largest of the sympathetic ganglia, measuring an inch or more in 

 length. 



Ganglion Cervicale Medius. The middle cervical ganglion is of small size, 

 is frequently absent, and may be divided into two parts. It is usually placed in 

 front of the inferior thyreoid artery as it passes behind the carotid sheath. 



Ganglion Cervicale Inferius. The inferior ganglion is joined by the con- 

 necting cord to the middle (or superior) ganglion above, and is only imperfectly 

 separated from the first thoracic ganglion below. It is of considerable size, 

 irregular in shape, and is placed behind the first part of the vertebral artery in 

 the interval between the last cervical transverse process and the neck of the first rib. 



The branches from the cervical sympathetic ganglia and connecting cords are 

 divisible into two sets (A) Central communicating branches for other nerves ; 

 (B) Peripheral branches of distribution, which alone, or along with other nerves, 

 form plexuses, accompanying and supplying vessels and viscera of thei head, neck, 

 and thorax. Although this distinction is made, it is to be borne in mind that 

 the branches of communication are as much nerves of distribution as the others. 



GANGLION CERVICALE SUPERIUS. 



Central Communicating Branches. 1. Gray rami communicantes pass from 

 the ganglion to the anterior rami of the first four cervical nerves. 



2. Communications with Cerebral Nerves. Just outside the skull, in the deep 

 part of the neck, communicating branches pass to the following cerebral nerves : (a] 

 to the petrous ganglion of the glossopharyngeal and the jugular ganglion of the 

 vagus ; (&) to the ganglion nodosum of the vagus ; (c) to the hypoglossal nerve. 



Peripheral Branches of Distribution. 1. Pharynx. Plexus Pharyngeus 

 Ascendens. A pharyngeal branch passes behind the carotid sheath to reach the 

 wall of the pharynx, where it joins (along with the pharyngeal branches of th( 

 glossopharyngeal and vagus nerves) in the formation of the ascending pharyngea. 

 plexus, and assists in supplying the muscles and mucous membrane of the pharynx 



