966 



THE NERVOUS SYSTEM 



cord, but, owing to the fact that in the later periods the vertebral column grows more rapidly 

 than the cord and increases considerably in length after the cord has practically ceased growing, 

 all the spinal nerves, wdth the exception of the first two, pass downward as well as outward. 

 The obhquity of their com'se from the level of attachment to the level of exit increases progres- 

 sively from above downward, and, as the cord ends at the level of the first or second lumbar 

 vertebra, the roots of the lower lumbar and of the sacral nerves pass at first vertically downward 

 within the dura mater, and form around the filum terminale a tapering sheaf of nerve-roots, 

 the Cauda equina (horse's tail) (fig. 613, p. 773). 



Topography of attachment. — The relations between the levels of attachment of 

 the spinal nerves to the cord and the spinous processes of the vertebrae situated 

 oppo-site these levels have been investigated by Nuhn and by Reid. The follow- 

 ing table compiled by Reid gives the extreme limits of attachment as observed in 

 six subjects. 



Table of Topography of Attachment of Spinal Nerves to the Spinal Cord. (Reid.) 



(A) signifies the highest level at which the root filaments of a given nerve ai-e attached 

 to the cord, and (B) the lowest level observed. For example, the root filaments of the sixth 

 thoracic nerve may be attached as high as the lower border of the spinous process of the second 

 thoracic vertebra, or some may be attached as low as the upper border of the spinous process of 

 the fifth thoracic vertebra, but in a given subject they do not necessarily extend either as high 

 or as low as either of the levels indicated. 



Nerves 

 Second cervical (A) A httle above the posterior arch of atlas. 



(B) Midway between posterior arch of atlas and spine of epistropheus. 

 Third " (A) A httle below posterior arch of atlas. 



(B) Junction of upper two-thirds and lower third of spine of epistropheus. 

 Fourth " (A) Just below upper border of spine of epistropheus. 



(B) Middle of spine of third cervical vertebra. 

 Fifth " (A) Just below lower border of spine of epistropheus. 



(B) Just below lower border of spine of fourth cervical vertebra. 

 Sixth " (A) Lower border of spine of third cervical vertebra. 



(B) Lower border of spine of fifth cervical vertebra. 

 Seventh " (A) Just below upper border of spine of fourth cervical vertebra. 



(B) Just above lower border of spine of sixth cervical vertebra. 

 Eighth " (A) Upper border of spine of fifth cervical vertebra. 



(B) Upper border of spine of seventh cervical vertebra. 

 First thoracic (A) Midway between spines of fifth cervical and sixth cervical vertebra. 



(B) Junction of upper two-thirds and lower third of interval between seventh 

 cervical and first thoracic vertebra. 

 Second " (A) Lower border of spine of sixth cervical vertebra. 



(B) Just above lower border of spine of first thoracic vertebra. 

 Third thoracic (A) Just above middle of spine of seventh cervical vertebra. 



(B) Lower border of spine of second thoracic vertebra. 

 Fourth " (A) Just below upper border of spine of first thoracic vertebra. 



(B) Junction of upper third and lower two-thirds of spine of third thoracic 

 vertebra. 

 Fifth " (A) Upper border of spine of second thoracic vertebra. 



(B) Junction of upper quarter and lower three-quarters of spine of fourth 

 thoracic vertebra. 

 Sixth " (A) Lower border of spine of second thoracic vertebra. 



(B) Just below upper border of spine of fifth thoracic vertebra. 

 Seventh " (A) Junction of upper third and lower two-thirds of spine of fourth thoracic 

 vertebra. 



(B) Just above lower border of spine of fifth thoracic vertebra. 

 Eighth " (A) Junction of upper two-thirds and lower third of interval between spines 

 of fourth thoracic and fifth thoracic vertebra. 



(B) Junction of upper quarter and lower three-quarters of spine of sixth 

 thoracic vertebra. 

 Ninth " (A) Midway between spines of fifth thoracic and sixth thoracic vertebra. 



(Bj LIpjx'r border of .spine of seventh thoracic vertebra. 

 Tenth " (A) Midw;iy betwe(>n spines of sixfli tlioracic and seventh thoracic vertebra. 



(B) Middle of the sj)ine of eighth thoracic vertebra. 

 Eleventh " (A) Junction of upi)er quarter and lower three-quarter.s of spine of seventh 

 thoracic vertebra. 



(B) Just aljove spine of ninth thoracic vertebra. 

 Twelfth " (A) Junction of uj)i)er (juartcr and lower three-quarters of spine of eighth 

 llioracic vertebra. 



(B) Just l>el()vv spine of ninth thoracic vertebra. 

 First lumbar (A) Midway Ix-twcen spines of eighth thoracic and ninth thoracic vertebrae. 



(B) Lower border of spine of tenth thoracic vertebra. 

 Second " (A) Middle of spine of ninth thoracic vertebra. 



(B) Junction of upper third and lower two-thirds of spine of eleventh thoracic 

 vertebra. 



