8 3 6 



THE CENTRAL NERVOUS SYSTEM 



marked are (i) The tract or tracts made up by the cells of the 

 anterior horn (Fig. 332), which practically run from end to end of the 

 cord, swell out in the cervical and lumbar enlargements, where the 

 cells are very numerous and of great size (70 p to 140 ft in diameter), 

 and contract to a thin thread in the thoracic region, where they are 

 relatively few, scattered, and small. In the enlargements there 

 are several groups of these cells corresponding with the segments 



of the limbs, the movements 



Sailings Cervical 

 nucleus 



Idtervl Cell column 

 inter- 



of the hand, forearm, and 

 upper arm being each repre- 

 sented by a group in the 

 cervical, and those of the foot, 

 leg, and thigh by groups in 

 the lumbar swelling. In the 

 rest of the cord only two 

 well-marked groups of cells 

 are present in the anterior 

 horn, a mesial and a lateral. 

 (2) Clarke's column, whose 



Stillings dorsal 



nucleus orCfarAe 

 Column 



Cells of 1hz date 

 Cornu 



tract) ce n s , mostly of good size and 



tract 



somewhat rounded in outline, 

 are situated at the inner side 

 of the root of the posterior 

 horn just where it joins on to 

 the grey cross-bar. It gradu- 

 ally increases in size from 

 above downwards, usually 

 'Scattered ceils Cff appearing first at the level of 

 " ' " the seventh or eighth cervical 

 nerve, attaining its maximum 

 development at the eleventh 

 or twelfth dorsal and dis- 

 appearing altogether, as a 

 continuous strand, at the level 

 of the second or third lumbar 

 nerves. Scattered nerve-cells, 

 however, constituting the so- 

 called cervical and sacral nuclei of Stilling, are frequently found 

 occupying the same position towards the upper and lower .ends of 

 the cord, and may be looked upon as isolated portions of Clarke's 

 column. (3) A tract of small cells called the intermedia-lateral 

 tract, lateral cell column, or lateral horn, situated at the outer edge 

 of the grey matter, about midway between the anterior and pos- 

 terior horns. It is best marked in the thoracic region, up to about 

 the second thoracic segment, although in the corresponding situa- 

 tion there are scattered cells in the lumbar swelling and the cervical 



StiUino's -Sacral 



si:: 



Fig. 332. Diagram of Grey Tracts of Cord. 



