CERVICAL GANGLIA 827 



each pair of sjdnal nerves. We find, lioweve^r, owing to the cohesion of certain 

 gangha, i)articularly in the cervical region, that the number is reduced to from 

 twenty to twenty-three })airs. In the tlioracic region the arrangement is the most 

 ty])ical, twelve j)airs of ganglia corresponding to the twelve thoracic nerves being 

 frequentlv present. In the thoracic region, also, the arrangement of the rami 

 communicantes is most easily studied. 



Each thoracic ganglion is connected with the anterior primary division of the 

 corresponding spinal nerve by two rami communicantes (fig. 470a), a white and 

 a grey. The white ramus consists of small medullated liljres which leave the 

 spinal cord by the anterior nerve root and pass to the ganglion. Some of the 

 fibres of the white ramus pass through the ganglion and leave the chain directly, 

 or more generally after running upwards or downwards for some distance within 

 it, by the rami efFerentes (fig. 470a). 



The rami cf^'crcntes pass to the prevertebral i)lexuses where they may end in 

 arborizations round the cells of the ganglia, or i)assing through these ganglionic 

 ]»lexuses they end round the cells of the terminal ganglia, which are situated either 

 close to or within the walls of the vessels and organs. Other fibres of the white 

 rami aflferentcs terminate round the cells of the vertebral ganglia (ganglia of the 

 chain). 



From the cells of the various ganglia, vertebral, ^prevertebral, and terminal, 

 non-medullated fibres arise which end in the walls of the viscera, vessels, and 

 glands. ^lany of the non-medullated fibres which issue from the thoracic verteljral 

 ganglia form the grey rami (fig, 470a). They pass to the spinal nerves. Some of 

 tliem turn inwards along the posterior nerve roots to the membranes of the spinal 

 cord and the walls of the spinal canal; others travel peripherally, with the branches 

 of the nerve; they terminate in the blood vessels, hair muscles, and skin glands. 

 The remaining non-medullated fibres, wdiich issue from the vertebral ganglia, leave 

 in the rami efferentes and pass through the prevertebral plexuses to their termina- 

 tions (fig. 470a). 



In addition to the fibres above mentioned, it is possible that there are also 

 afferent (sensory) fil)res passing from the viscera, glands, and vessels through the 

 sympathetic ganglia to the posterior nerve roots and thence to the spinal cord. 



Cranial portion of the sympathetic. — The small sporadic ganglia (ophthalmic, spheno-jiala- 

 tine, otic, and submaxillary), which have already been described in connection with the tri- 

 geminal neiTC, are regarded by some anatomists as representing a cranial portion of the gangliated 

 cord, and sympathetic fibres are undoubtedly given off from the ninth, tenth, and eleventh cranial 

 nerves. 



CERVICAL PORTION OF THE GANGLIATED CORD 



The cervical portion of the gangliated cord consists of three ganglia united 

 by intervening nerve-cords. Of these the superior cervical ganglion is the largest, 

 and probal)ly represents four coalesced ganglia; the middle cervical ganglion is the 

 smallest, and represents two ganglia; the inferior, intermediate in size, is probably 

 formed by the union of two ganglia. The cord takes a vertical course down the 

 neck, and is in contact posteriorly with the prevertebral layer of the cervical fascia. 

 Behind this fascia it corresponds to the rectus capitis anticus major above, and the 

 longus colli below. These muscles and the prevertebral fascia intervene between 

 tlie cord and the transverse processes of the cervical vertebrcT. The internal carotid 

 above, and the common carotid artery below, are j)laced in front of the gangliated 

 cord, and the pneumogastric nerve is external to it. 



Superior Cervical Ganglion 



The superior cervical ganglion is a fusiform body, about one inch to an inch 

 and a half in length (2.5 to o.75 cm.). It corresponds to the transverse processes 

 of the second and third (and sometimes the first) cervical vertebra\ Al)Ove, it is 

 continued into a stout trunk which is called the ascending branch. Below, it ends 

 in a cord which passes downwards to join the middle cervical ganglion. It is con- 

 nected to the anterior primary divisions of the four upi)er cervical nerves by as 



