752 



NEUROLOGY 



presents two swellings or enlargements, an upper or cervical, and a lower or lumba r 

 (Fig. 663). 



The cervical enlargement is the more pronounced, and corresponds with the attach- 

 ments of the large nerves which supply the upper limbs. It extends from about 

 the third cervical to the second thoracic vertebra, its maximum circumference 

 (about 38 mm.) being on a level with the attachment of the sixth pair of cervical 

 nerves. 



The lumbar enlargement gives attachment to the nerves which supply the lower 

 limbs. It commences about the level of the ninth thoracic vertebra, and reaches 

 its maximum circumference, of about 33 mm., opposite the last thoracic vertebra, 

 below which it tapers rapidly into the conus medullaris. 



Fissures and Sulci (Fig. 664). An anterior median fissure and a posterior 

 median sulcus incompletely divide the medulla spinalis into two symmetrical 

 parts, which are joined across the middle line by a commissural band of nervous 

 matter. 



Posterior median sulcus 



Posterior median septum 





Posterior 

 terve roots 



'ostero-lateral sulcus 



Posterior 

 column 



Formaiio 

 reticularis 

 Lateral 

 column 



Anterior 

 column 



Anterior nerve roots Anterior median fissure 

 FIG. 664. Transverse section of the medulla spinalia in the mid-thoracic region. 



The Anterior Median Fissure (fissura, mediana anterior) has an average depth of 

 about 3 mm., but this is increased in the lower part of the medulla spinalis. It 

 contains a double fold of pia mater, and its floor is formed by a transverse band 

 of white substance, the anterior white commissure, which is perforated by blood- 

 vessels on their way to or from the central part of the medulla spinalis. 



The Posterior Median Sulcus (sulcus medianus posterior) is very shallow; from it 

 a septum of neuroglia reaches rather more than half-way into the substance of the 

 medulla spinalis; this septum varies in depth from 4 to 6 mm., but diminishes 

 considerably in the lower part of the medulla spinalis. 



On either side of the posterior median sulcus, and at a short distance from it, 

 the posterior nerve roots are attached along a vertical furrow named the postero- 

 lateral sulcus. The portion of the medulla spinalis which lies between this and the 

 posterior median sulcus is named the posterior funiculus. In the cervical and upper 

 thoracic regions this funiculus presents a longitudinal furrow, the postero-inter- 

 mediate sulcus ; this marks the position of a septum which extends into the posterior 

 funiculus and subdivides it into two fasciculi a medial, named the fasciculus 

 gracilis (tract of Goll); and a lateral, the fasciculus cuneatus (tract of Burdach) 



