SPINAL COED AND NERVES 



280 



already said that the fibres of the dorsal columns are the direct 

 continuation of the dorsal roots, which originate in the cells of 

 the spinal ganglia. The fibres of the tract of Goll are small 

 in diameter, and many of them, instead of entering the grey 

 matter of the cord, run as far as the medulla oblongata, where 

 they terminate in a special nucleus of grey matter (nucleus of 

 the funiculus gracilisj. The tract of 

 Burdach consists of larger fibres which 

 send numerous collaterals to the grey 

 matter, and penetrate into it after a longer 

 or shorter course, coming into intimate 

 relation with the cells of Clarke's column. 

 Both these tracts undergo ascending de- 

 generation after section or compression of 

 the cord, or severance of the dorsal roots. 

 Goll's tract, which is myelmated later, 

 contains the longer paths which arise 

 from the lumbo-sacral and lower thoracic 

 roots ; while Burdach's tract, for the most 

 part, consists of short intraspinal paths, 

 with longer fibres derived from the higher 

 thoracic and cervical roots, which do not 

 enter the tract of Goll, and terminate in 

 the nucleus of the funiculus cuneatus or 

 nucleus of Burdach in the bulb. Thus 

 the two bundles of the dorsal column are 

 composed principally of exogenous fibres 

 or spino-cerebral paths of conduction, but 

 they also contain endogenous fibres or 

 intraspinal paths. 



(e) The endogenous intraspinal fibres 

 are represented mainly by the portions 

 of the white matter adjacent to the grey. 

 Such is probably the character of the zone F io. ivT.-As^ndm,^ degeneration 

 of fine fibres which fills the area between 

 the ventral and dorsal horns, termed by cowers, after 

 Sherrington and Grlinbauni the lateral 

 limiting layer (Fig. 178, I. n. 5). But a 



certain number of intraspinal fibres with a short course are inter- 

 spersed among the fibres of the crossed pyramidal tract. They 

 are distinguished from the latter by their earlier myelination, and 

 by the fact that they do not degenerate with them (Miinzer). 



The so-called ground bundle of the ventro- lateral column 

 occupies a sectional area that varies with the area of the grey 

 matter. Probably many of its fibres are interspinal and serve to 

 connect the grey matter of different segments of the cord. 



The ventral zone of the dorsal column consists of fibres whose 



the 



cord at the 1st liiinluii 1 

 m^nt. (Gowers.) 



VOL. Ill 



u 



