126 ELEMENTARY PHYSIOLOGY. [XXX. 



14. In front of the anterior joined ends of the ex- 

 ternal convolutions is a deep fissure (the supra- 

 orbital) ; the part of the brain in front of this is 

 called the sub-orbital lobe. 



15. Cut away the first convolution and note the 

 surface of the cortex, island of Reil, lying at 

 the bottom of Sylvian fissure. 



D. HISTOLOGY. 



1. Cut transverse sections of the spinal cord just 

 above the origin of the 1st cervical nerve, at the 

 beginning of the decussation of the pyramids. 

 Note 



a. The anterior and posterior cornua of the 

 grey substance are partially separated from 

 one another by bundles of medullated fibres 

 springing from the lateral columns and ex- 

 tending some little distance in the grey sub- 

 stance towards the median line. 



1). Some oblique bundles of fibres will be seen 

 running through the grey matter on either 

 side and crossing in front (ventrally) of the 

 grey commissure, forming part of the decus- 

 sation of the pyramids. 



c. Medially of the anterior column will be seen 

 a thin band of transversely cut small fibres ; 

 these are the fibres which have already 

 crossed, the beginnings of the anterior pyra- 

 mid. 



