XXIX.] SPINAL CORD. 307 



a. The single unbranched axis-cylinder process. 



b. The numerous remaining processes (proto- 

 plasmic processes) frequently branching, some 

 may be seen to divide into very fine fibrils. 



6. Cut an antero-posterior longitudinal section 

 passing through both the anterior and the pos- 

 terior nerve-roots. Note 



a. The longitudinal medullated fibres of the 

 anterior column. 



b. The anterior nerve-roots entering obliquely. 



c. The nerve-cells and fibres of the anterior 

 cornu. 



d. The substantia gelatinosa of the posterior 

 cornu, with vertical fibres on either side and 

 curved fibres running through it. 



e. The longitudinal medullated fibres of the 

 posterior columns, in which can be seen 



/. The cut ends of the posterior nerve-roots. 



DEMONSTRATION. 



Section of spinal cord prepared by "Weigert's 

 method to show medullated fibres in the grey 

 substance. (Cf. p. 39 G). 



202 



