340 



ANATOMY OF THE CENTRAL NEBVOUS SYSTEM. 



fined groups of the cervical portion and those of tlie lumbar cord, containing espe- 

 cially numerous cells, are less developed in the dorsal part of the cord, corresponding 

 to its smaller volume and perhaps also to the difi'erent functions of the nerves 

 arising from it. 



None of these groups, e.xcepting, perhaps, the posterior median group, can be 

 followed continuously throughout the cord. There is much to indicate that this 

 group serves to innervate the muscles of the back. As seen in the tables on pages 

 336 and 337, the brachial plexus arises from the cervical cord. For its various 

 elements a thorough investigation of all the cases in which loss of function was 

 present as a symptom of spinal disease (Kayser, Collins) points out the nuclei. 



Fig. 218. — From the anterior border of ii cross-section of the anterior gray 

 horn. Transition of a cell-process into the anterior root. Carmine preparation 

 "%• (After Henle.) 



From the lateral group in the cervical cord come the flexor nerves, from the more 

 median group those for the extensors of the arm and the hand. 



The roots of the sensor]' nerves enter, after passing through the spinal 

 ganglia, partly direct in the posterior horn, parti}' in the posterior white 

 colnmns. The cells of the spinal ganglion form the sonrces of the majority 

 of these fibers. It will be remembered that, as embryology teaches, the axis- 



