CHAP, v.] 



THE SPINAL CORD. 



599 



with which the motor fibres of the nerves of the leg are specially 

 connected, and induce such changes in this grey matter as to lead 

 to the discharge of the appropriate impulses along those motor fibres. 

 And such a view is strongly supported by the anatomical fact, as 

 illustrated by Figs. 78 -80, that along the length of the spinal cord, 

 the amount of grey matter varies according to the number of fibres 

 passing into the cord, indicating that the fibres as they pass into the 

 cord have a certain amount of grey matter allotted to them. More- 

 over, though the course which the fibres of the posterior roots take 

 immediately upon entering the cord has perhaps yet not been 

 satisfactorily determined, the fibres of the anterior root have been 

 definitely traced to the nerve cells of the anterior cornu; and 

 according to recent observations, in the frog at all events, the 

 cells of the anterior cornu are equal in number to the fibres of the 

 anterior root. 



I XII XI X IX VIII VII VI V IV III II I VIII VII VI V IV III U 



FIG. 78. DIAGRAM SHEWING THE RELATIVE SECTIONAL AREAS OF THE SPINAL NERVES, 



AS THEY JOIN THE SPINAL COBD. 



V IV II! II I V IV III II I XI XI X IX VIII VII VI V IV III II I VIII VII VI V IV III II I 



FIG. 79. DIAGRAM SHEWING THE UNITED SECTIONAL AREAS OP THE SPINAL NERVES, 

 PROCEEDING FROM BELOW UPWABDS. 



V IV III II I V IV III II I XII XI X IX Viil VII VI V IV III II I via VII VI V IV HI II I 



FIG. 80. DIAGRAM SHEWING THE VARIATIONS IN THE SECTIONAL AREA OF THE GREY 

 MATTER OF THE SPINAL CORD, ALONG ITS LENGTH. 



All three figures are to read from left (the bottom of the cord) to right (top of 

 the cord), the numerals indicating successively the sacral, lumbar, dorsal and 

 cervical nerves. The figures are not drawn to the same scale. 



