THE SPINAL CORD 



649 



ventral dianu'tcr is also slip;htly smaller. Behind this the cord tapers rapidly to 

 form the conus medullaris. The tip of the latter is continued by a delicate glisten- 

 ing strand, the filum terminale, which is composetl largely of fibrous tissue con- 

 tinued from the pia mater, covered by 

 arachnoid. 



The surface of the spinal cord is 

 divided into two similar halves by a 

 dorsal median groove (Sulcus medianus 

 dorsalis) and a ventral median fissure 

 (Fissura mediana ventralis). On either 

 side of the former is the dorso-lateral 

 groove (Sulcus dorsalis lateralis) at 

 which tlu> fibers of the dorsal nerve- 



Fio. 496. — Cauda Equina. 

 ] , Dura and arachnoidea divided and reflected; 

 ;2, spinal cord; cJ, nerve-roots. (From Leisering's Atlas, 

 reduced.) 



roots enter the cord; it is faint except 

 at the enlargements, and is represented 

 by tAvo grooves in the first cervical 

 segment. The ventral root-fibers as 

 they emerge from the cord do not 

 form a continuous series, but arise 

 from a zone (Area radicularis ven- 

 tralis) 3 to 5 mm. in width a little lateral to the ventral median fissure, 

 and no groove is found here. In the greater part of the cervical region and 

 the anterior part of the thoracic region there is a shallow dorsal paramedian 

 groove (Sulcus intermedins dorsalis) a short distance lateral to the median 



Fig. 495. — Vkntrai. View of Medulla Oblongata 

 .\ND First and Second Segments of Spinal 

 Cord of Horse; the Membranes are Cut 

 AND Reflected. 



/, Lig. suspensorium arachnoideale; 2, right 

 cerebrospinal artery; S, 5, digitations of lig. denticu- 

 latum; 4, free border of lig. denticulatum; 6, middle 

 spinal artery; 7, basilar artery; 8, pons; 9, arach- 

 noidea; 10, dura mater; 11. 13, ventral root-bundles 

 of first and second segments of spinal cord; 1'/., N. 

 abducens; IX, X, glosso-pharyngeus and vagus; XI, 

 accessory, medullary part; A'/', accessory, spinal part; 

 a, line between medulla oblongata and spinal cord. 

 (Dexler, in EUenberger-Baum, Anat. d. Haustiere.) 



