Till-: SI'IXAL CORD 



761 



right unil left halves by the broad anterior median fissure into which tin; pin mater 

 is duplicated, And opposite this, on the dorsal surface, by the posterior median sul- 

 cus. Along the lower two-thirds of the cord this sulcus is merely a septum; in the 

 medulla oblongata it opens up and attains the character of a fissure, and finally 

 becomes continuous into the fourth ventricle. Kach of the two lateral halves of 

 the cord is marked off into a posterior, lateral, and anterior division by (wo other 

 longitudinal sulci. ( )f these, the postero-lateral sulcus occurs as a Blight groove 

 '2 to ,'H mm. lateral from the posterior median sulcus. and is the groove in which the 

 dorsal roots enler (he cord in regular linear series. The ventral division is separated 

 from the lateral by the antero-lateral sulcus. This is rather an irregular, linear 

 area than a sulcus. It is from 1 to 2 mm. broad, and represents the area along 

 which t lie efferent fibres make their exit from the cord to be assembled into the respec- 

 tive ventral roots. This area varies in width according to the size of the nerve-roots. 

 and, like the postero-lateral sulcus, its distance from the mid-line varies according 

 to locality, being greatest on the enlargements of the cord. In the cervical region, 

 and in part of the thoracic, the posterior division is subdivided by a delicate longi- 

 tudinal groove, the postero-intermediate sulcus, which becomes more evident 

 towards the medulla oblongata and represents the line of demarcation between the 

 fasciculus gracilis and the fasciculus cuneatus. Occasionally in the upper cervical 



FIG. 568. A, VENTRAL, AND B, DORSAL, VIEWS OF PORTION OF SPINAL CORD SHOWING MODES OP 

 ATTACHMENT OF DORSAL AND VENTRAL ROOTS. 



ANTBRO-LATKRAL Sn.W.1 (tint of rtnlral roo) 



FILA RAVICl'LARIA 



DORSAL ROOT 

 \ 

 YKXTRAl. ROOT 



X/TVI/. <:\X<ll.IA 



region a similar line may be seen along the ventral aspect close to the anterior 

 median fissure. This is the antero-intermediate sulcus, forming the lateral 

 boundary of the ventral pyramidal fasciculus. 



Collectively, the entire space between the posterior median sulcus and the line of 

 attachment of the dorsal roots is occupied by the posterior funiculus; the lateral 

 space between the line of attachment of the dorsal and that of the ventral roots, 

 by the lateral funiculus; and the space between the ventral roots and the anterior 

 median fissure, by the anterior funiculus. Kach of these funiculi is subdivided 

 into its component fasciculi. 



The dorsal and ventral nerve-roots are not attached to the cord as such, but are 

 first frayed out into numerous thread-like bundles of axones which are distributed 

 along their lines of entrance and exit. These bundles are the root filaments (fila 

 radicularia) of the respective roots. The fila of the larger spinal nerves are fanned 

 out to the extent of forming almost continuous lines of attachment, while in the 

 thoracic nerves there are appreciable intervals between those of adjacent -roots. 

 Throughout, the intervals are less between the fila of the ventral than between 

 those the dorsal roots. 



Internal structure of the spinal cord. By reflected light masses of medul- 

 lated axones appear white, and such masses are known as white substance. Masses 



