SURFACE OF SPINAL CORD 



773 



more than a line which marks the position of the posterior median septum; in 

 the medulla oblongata it opens up and attains the character of a fissure. Each 

 of the two lateral halves of the cord is marked off into a posterior, lateral and 

 anterior division by two other longitudinal sulci. Of these, the postero-lateral 

 sulcus occurs as a slight groove 2 to 3^ mm. lateral from the posterior median 

 sulcus, and is the groove in which the root filaments of the dorsal roots enter the 

 cord m regular linear series. The ventral division is separated from the lateral 



Fig. 613.— Drawing from Specimen showing Cauda Equina, the Roots of Certain of 



THE bPINAL ^ ERVES WHICH FORM IT, AND ITS ACCOMPANYING DuRA MaTER. (Dorsal aspect.) 



\. 



-Dura mater spinalis 



Lumbar enlargement 



Conus medullaris 



Filtim terminale 



Coccygeal ligament (filum 

 duree matris spinalis) 



by the antero -lateral sulcus. This is rather an irregular, linear area than a 

 ^^^^^'. J* ^s ^^0^ 1 to 2 mm. broad, and represents the area along which the 

 enerent fibres make their exit from the cord to be assembled into the respective 

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

 and, fike 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 along a part of the thoracic, the posterior division is subdivided by a delicate 

 longitudinal groove, thepostero-intermediate sulcus, which becomes more evident 



