THE NERVOUS SYSTEM. 



93 



The multipolar cells are either scattered singly or arranged in groups, of 

 which the following are to be distinguished: (a.) In the anterior cormi. 

 The groups found in the anterior cornu are generally two one at the 

 lateral part near the lateral column, and the other at the tip of the cornu 

 in the middle line sometimes, as in the lumbar enlargement, there is a 

 third group more posterior. The cells of the anterior group are the 

 largest. Into many of these cells the fibres of the anterior motor nerve- 

 roots can be distinctly traced, (b.) In the tractus inter medio-lateralis. 

 A group of nerve-cells midway between the anterior and posterior cornua, 

 near the external surface of the grey matter. It is especially developed 

 in the dorsal and also in the upper cervical region, (c. ) In the posterior 



FIG. 318. Transverse section of half the spinal cord in the lumbar enlargement (semi-diagramma- 

 tic). 1. Anterior median fissure; 2, posterior median fissure; 3, central canal lined with epithelium; 

 4. posterior commissure ; 5, anterior commissure ; 6, posterior column ; 7, lateral column ; 8, anterior 

 column. The white substance is traversed by radiating trabeculae of pia mater. 9. Fasciculus of 

 posterior nerve-root entering in one bundle ; 10, fasciculi of anterior roots entering in four spreading 

 bundles of fibres ; 6, in the cervix cornu, decussating fibres from the nerve-roots and posterior com- 

 missure ; c, posterior vesicular columns of Lockhart Clarke. About half way between the central 

 canal and 7 are seen the group of nerve-cells forming the tractus intermedio-lateralis ; e, e, fibres of 

 anterior roots; 

 son.) x 



7 are seen the group of nerve-cells forming 



oots; e', fibres of anterior roots which decussate in anterior commissure. (Allen Thom- 



trvicnlar columns of Lockhart Clark. These are found in the posterior 

 cornua of grey matter toward the inner surface, extending from the cer- 

 vical enlargement to the third lumbar nerves (Fig. 318, c). (d.) Smaller 

 cells are scattered throughout the grey matter, but are found chiefly at 

 the tip (caput cornu) of the posterior cornu, in a finely granular basis, 

 and among the posterior root fibres (substantia gelatinosa cinerea of 

 Rolando). 



The nerve-cells are connected by their processes immediately with the 

 axis-cylinder of the fibres of the anterior or motor nerve-roots: whereas 

 the nerve-cells of the posterior roots are connected with nerve-fibres, not 



