THE SPINAL MEDULLA. 



525 



In the lower part of the conus medullaris the gray matter in each half of 

 the spinal medulla assumes the form of an oval mass joined to its fellow of the 

 opposite side by a thick gray commissure. Here, almost the entire bulk of the 

 spinal medulla consists of 'gray matter, seeing that the white matter is reduced to 

 such an extent that it forms only a thin coating on the outside. 



White Matter of the Spinal Medulla. In transverse sections of the spinal 

 medulla the three funiculi into which the white matter is subdivided become very 



Posterior median septum 



Septum 

 p. erior lateral groove 



'osterior nerve-root 



ubstantia 



jelatinosa 



,oot-tibres 



e iring gray 



matter 



Processus 



eticularis 



sntral 

 canal 



l ;erior nerve-root 



Interior median 



fissure-^ 



Posterior median 

 septum 



Posterior lateral 

 groove 



Posterior colu 



Dorsal nucleui 

 Lateral colum 

 Central canal 



Anterior colui 



nterior median 

 fissure 



B. Through the mid -thoracic region. 



L. Cervical region at the level of the fifth cervical nerve. 

 (From a specimen prepared by Dr. A. Bruce.) 



median 

 septum 

 Substantia 

 gelatinosa 

 Root-fibres enter- 

 ing gray matter 



Central \X>, 

 canal ./$ 



Anterior whitei 



commissure n 



Nuclei of origin 



T'nnu which the 



motor-fibres 



for muscles of 



the lower limb 



arise 



Anterior nerve - 

 root 

 median 

 'fissure 





Through the lumbar region at the level of the 

 fourth lumbar nerve. 



FIG. 467. SECTION THROUGH EACH OF THE FOUR REGIONS OF 

 prepared by the Weigert-Pal method ; therefore the white 

 gray matter is bleached. ) 



Posterior median 

 septum 



Posterior 

 nerve-root. 



Substantia 

 gelatinosa 



Posterior gray 

 commissure 



Anterior white 

 commissure 



Anterior median 

 fissure 



D. Through the sacral region at the level of the 

 third sacral nerve. (From a specimen pre- 

 pared by Dr. A. Bruce. ) 



THE MEDULLA SPINALIS. (From specimens 

 matter is rendered dark in colour whilst the 



apparent. The posterior funiculus is wedge-shaped, and lies between the posterior 

 median septum and the posterior column of gray matter. The lateral funiculus 

 occupies the concavity of the gray crescent. Behind, it is bounded by the posterior 

 column of gray matter and the sulcus lateralis posterior, whilst in front it extends 

 as far as the most lateral fasciculi of the anterior nerve-roots as they pass out from 

 the anterior column. The anterior funiculus includes the white matter between the 

 anterior median fissure and the anterior column of gray matter, and also the white 



