MINUTE STRUCTURE OF THE CORD. 



511 



connective tissue is remarkably abundant, and the nerve-fibres particularly small. 

 The connective tissue forms also a reticulum (processus reticularis), in which the 

 longitudinal nerve-fibres are imbedded. In the grey matter the connective tissue is 

 still more abundant, more especially in the immediate neighbourhood of the central 

 canal. Much discussion has taken place as to whether the smallest cells already 

 described are really nervous or belong to the connective tissue. In the present 

 imperfect state of knowledge of the development of nervous elements, it might be 

 rash to express a decided opinion on this point ; but it may be stated that, independently 

 of these, nuclei are figured by Kolliker in the reticulum, and also cells containing 

 numerous and dividing nuclei in the neighbourhood of the central canal. 



Origin of the spinal nerves. The anterior and posterior roots of the spinal nerves 

 are attached along the sides of the cord in or near the anterior and posterior lateral 

 grooves, and opposite to the corresponding cornua of the grey matter ; the posterior 

 roots in a straight line, and the anterior roots scattered somewhat irregularly upon 

 the surface (Fig. 345). 



The fibres of the anterior roots may be traced into and through the anterior 

 cornua. They then diverge in different directions. The innermost fibres, after 

 passing through among the cells in the inner group of the anterior cornu, cross in the 

 white commissure to the anterior column of the opposite side. Many fibres pass 

 backwards in the substance of the anterior cornu, where some of them would appear 

 to form connection with fibres proceeding from other parts of the cord, and others to 

 spread obliquely upwards and downwards ; while those which are most external 

 passing through the outer group of cells, reach the lateral column. 



Fig. 347. A SMALL FOR- Fig. 347. 



TION OF A TRANSVERSE 

 SECTION OP THE SPINAL 

 CORD AT THE PLACE 

 WHERE TWO BUNDLES OP 

 THE FIBRES OF THE 

 ANTERIOR ROOTS PASS 

 INTO THE GREY SUB- 

 STANCE. ^P 



This figure may be looked 

 upon as representing the 

 inner ends of the anterior 

 roots of the nerves, of 

 which the outer part is 

 shown in fig. 346. a, a, 

 the two bundles of fibres of 

 the anterior root passing 

 between the compartments 

 of longitudinal fibres of the 

 cord ; b, b, these fibres 

 running backwards through 

 the grey substance towards 

 the posterior cornua ; c, c', 

 those spreading in the anterior cornua on the one side towards the anterior commissure, 

 and on the other round the outer side of the anterior cornu ; d, d, portions of three com- 

 partments of the anterior columns in which the longitudinal fibres of the cord are shown 

 in transverse section ; e, e, large radiated and nucleated cells in the grey substance of the 

 anterior cornu some with three, others with a greater number of processes emanating 

 from them : no direct communication is shown between these processes and the nerve 

 fibres of the roots. 



The fibres of the posterior roots on reaching the posterior cornu diverge from each 

 other in a curved manner, so as to form in great part the substantia gelatinosa. In 

 front of this there may be seen, cut across in transverse sections, a group of these 

 fibres which turn longitudinally upwards and downwards, and afterwards pass 

 forwards, in part at least, to the anterior cornu, and in part to reach by the posterior 

 commissure the posterior and lateral columns of the opposite side. Other fibres of 

 the posterior roots pass forwards at once through the grey substance to the anterior 



