58 TOPOGRAPHICAL ANATOMY OF THE 



From the first thoracic ganglion also arises a nerve cord that can be 

 followed alon<j; the dorsal wall of the thorax, over the edge of the 

 diaphragm (between one of its crura aod the psoas minor muscle), and 

 into the abdomen. At first tlie cord occupies a groove at the border of 

 the longns colli muscle, but later it runs across the heads of the ribs and 

 the intercostal vessels immediately underneath the pleura. 



Ganglia on the cord, at first small and inconstant but afterwards 

 larger, begin about the third or fourth intercostal space and occur, one 

 at each space, throughout the rest of the thorax. Each ganglion is 

 connected with the ventral primary branch of the corresponding spinal 

 nerve by means of a communicating branch, the ramiLS cominiiiiicans. 



Numerous delicate filaments leave the ganglia to join the fine 

 plexuses associated with the aorta and oesophagus. Two nerves of 

 greater size are known as the splanchnic^ nerves. 



The greater splanchnic nerve (n. splanchnicus major) begins as 

 a filament detached from the sixth or seventh - thoracic ganglion. 

 Accompanying the sympathetic cord (to which it is generally medial) 

 along the vertebral column, the nerve receives contributions from the 

 succeeding ganglia up to and including the fifteenth or sixteenth. It 

 enters the abdomen by passing between the psoas minor muscle and a 

 crus of the diaphragm, and therein joins the combined coeliac and 

 cranial mesenteric ganglia. 



The lesser splanchnic nerve (n. splanchnicus minor) is composed of 

 filaments derived from the last two or possibly three thoracic ganglia. 

 This nerve also enters the abdomen and joins the coeliac or the renal 

 plexus. 



M. LONGUS COLLI. — Only a part (pars thoracalis) of the longus colli 

 muscle can be dissected at the present time. It forms a rounded mass 

 of muscular fibres springing from the bodies of the first five or six 

 thoracic vertebra?, and it is inserted by a strong tendon into the bodies 

 and transverse processes of the last two cervical vertebra?. A synovial 

 bursa lies betvveen the tendon and the vertebral column about the 

 junction of the last cervical and the first thoracic vertebrae. 



Dissection.- — The remains of the muscles should be cleared away from 

 the vertebrae and ribs in order that the joints and ligaments may be ex- 

 amined. Before the articulations can be studied in a thorough manner, 

 it is necessary to open the vertebral canal and I'cmove the spinal cord. 

 Though the cord and its covering membranes (which must be left intact) 

 should be laid aside for examination at a future time, the origins of the 

 spinal nerves — so far as they can be seen without opening the stout, 



' cr7rXa7xiKcis (.splaiichnicos) [Gr.], pertaining to viscera {airXdyx^o^ (splauclmon) 

 a vi.«cus). 



2 Throughout tlie above enuineralion, a thoracic ganglion is named in agreement 

 with tlie thoracic spinal nerve witli which it is connected. 



