STRUCTURE OF THE SPINAL CORD 191 



In the dorsal region the grey matter is small in amount, and both 

 cornua are slender (D 5). The whole cord is smaller in diameter than 

 either in the cervical or lumbar region. The column of nerve-cells 

 known as Clarke's column, and the intermedio-lateral tract, are well 

 marked. 



In the lumbar region the crescents of grey matter are very thick, 

 and the white substance, especially the lateral columns, relatively small 

 in a.mount (L 5). The isthmus lies nearly in the centre of the cord, 

 whereas in the cervical and dorsal regions it is nearer the anterior 

 surface. The posterior median columns are not seen. 



In the part of the spinal cord from which the sacral and coccygeal 

 nerve-roots take origin the grey matter largely preponderates, the 

 crescents forming thick irregular masses, and the grey isthmus being 

 also of considerable thickness. 



