THE m:r\ous system 



477 



7? 



(4) A Cerebral or Pallial Arc: (a) Peripheral afferent neurones, 

 via long ascending arms to (b) nucleus gracilis or cuneatus, thence as 

 medial lemniscus to (c) 

 thalamus to cortex 

 pallii; (d) associative 

 neurones of cortex; (e) 

 cortical precentral neu- 

 rones via pyramid to 

 (/") efferent peripheral 

 neurones to effectors. 

 Another arc would in- 

 volve the spino-thala- 

 mic tract instead of the 

 lemniscus. (Figs. 330 

 and 331.) 



Similar arcs ma}' in- 

 clude efferent sympa- 

 thetic neurones. (See 

 pp. 471 and 442.) 



TECHNIC 



(i) Carefully remove the 

 cord (human if possible; if 

 not, that of a large dog) 

 with its membranes, cut 

 into two or three pieces if 

 necessary, and lay on sheet 

 cork. Slit the dura along 

 one side of the cord, lay the 

 folds back, and pin the dura 

 to the cork. Care must be 

 taken to leave the dura very 

 loose, otherwise it will flat- 

 ten the cord as it shrinks 

 in hardening. With a 

 sharp razor now cut the 

 cord, but not the dura, into 

 segments about i cm. thick. 

 Fix in Orth's fluid (p. 7). 

 Pieces of the cord may be 

 cut out as wanted and em- 

 bedded in celloidin. Sec- 

 tions should be cut about 

 i5.« in thickness. 



