COMPEESSION OF THE SPINAL COED. 227 



TABLE OP LEVELS OF ORIGIN AND EXIT OP SPINAL NERVES continued. 



Roots. Level of Origin from Cord. Point of Exit from Canal. 



D. 8 ... Ranges from top of 5th to top of 6th dorsal 



spine ... ... Above 9th dorsal vert. 



9 ... Ranges from midway between 5th and 6th 



to top of 7th dorsal spine Above 10th dorsal vert. 



10 ... Ranges from midway between 6th and 7th 



to middle of 8th dorsal spine Above llth dorsal vert. 



11 ... Ranges from top of 7th to top of 9th dorsal 



spine ... ... ... Above 12th dorsal vert. 



12 ... Ranges between top of 8th and bottom of 



9th dorsal spine ... ... Above 1st lumbar vert. 



L. 1 ... Ranges from top of 9th to bottom of 10th 



dorsal spine ... ... Above 2nd lumbar vert. 



2 ... Ranges between 9th and llth dorsal spines Above 3rd lumbar vert. 



3 ... Ranges between top of 10th and bottom of 



llth dorsal spine ... ... ... ... Above 4th lumbar vert. 



4 ... Ranges between bottom of 10th and top of 



12th spine ... ... ... Above 5th lumbar vert. 



5 ... Ranges between top of llth and middle of 



12th dorsal spine ... ... ... ... Above 1st sacral vert. 



S. 1 ... Ranges between lower border of llth dorsal 



spine and top of 1st lumbar spine ... Above 2nd sacral vert. 



2 ... Usually between 12th dorsal and 1st lumbar 



spines ... ... ... Above 3rd sacral vert. 



3 ... Usually between 12th dorsal and 1st lumbar 



spines Above 4th sacral vert. 



4 ... Usually between 12th dorsal and 1st lumbar 



spines ... ... ... ... ... Above 5th sacral vert. 



5 ... At lower border of 1st lumbar spine ... Above coccyx. 

 Coccygeal... Between lower border of 1st and upper 



border of 2nd lumbar spines 



Summary. 



The eight cervical nerves arise from the cord between the occiput and the sixth 

 cervical spine. 



The upper six dorsal nerves between the sixth cervical and the fourth dorsal 

 spines. 



The lower six dorsal nerves between the fourth and ninth dorsal spines. 



The five lumbar nerves arise between the ninth and twelfth dorsal spines. 



The five sacral nerves opposite the twelfth dorsal and first lumbar spines. 



COMPRESSION OF THE SPINAL CORD. 



'The spinal cord, being suspended in the spinal canal, is liable 

 to compression, bruising, or laceration in fracture-dislocations of 

 the vertebral column. Moreover, the bony unyielding character 

 of the neural canal renders compression almost inevitable when 

 inflammatory or malignant disease extends into the cavity from 

 the adjacent vertebrae, or arises in the spinal membranes. The 

 dural sheath of the cord is separated from the surrounding bones 



152 



