STRUCTURE OF THE GREY SUBSTANCE OF THE SPINAL CORD. 349 



process appears homogeneous, whilst the branched processes 

 present a finely granular appearance : this difference between 

 the two processes has however lost its significance, since it has 

 been shown by M. Schultze that, when perfectly fresh, both 

 the unbranched as well as the branched processes possess a 

 finely fibrillar structure. At a variable distance from the nerve 

 cell the undivided process becomes invested by medulla, and is 

 thus converted into a true centric nerve fibre with medullary 

 sheath and axis-cylinder, which last is formed by the un- 

 branched nerve process itself. What becomes of this fibre that 

 clearly originates from the nerve cell, whether it ascends in 

 the white columns to the brain, or whether it constitutes a 

 root fibre of one of the spinal nerves, has not at present been 

 accurately determined. 



Deiters took the latter view, and hence named the un- 

 branched process the " nerve process," whilst he conferred the 

 less happily selected name of " protoplasmic processes " to the 

 Mnbranched processes, to which, however, as it has once been 

 given, we shall adhere. 



Three questions arise for the unprejudiced observer in regard 

 to these processes : 1, What direction does the nerve process 

 follow, and what is its ultimate destination? 2, What becomes 

 of the protoplasmic processes ? and, 3, Do all the cells of the 

 spinal cord possess nerve processes, or are there any that give 

 off protoplasmic processes alone ? 



As regards the first question, it was decidedly a happy 

 thought of Deiters to associate the nerve process of the cells 

 with the origin of the nerves of the spinal cord. For even if 

 the relations between them prove to be not quite so simple as 

 Deiters supposed, who considered that the fibres of the ante- 

 rior roots originated in the cells of the anterior cornu, and 

 those 'Of the posterior roots from the cells of the posterior 

 cornu, it may nevertheless be stated with an approximation 

 to certainty that Deiters' statement is correct in regard to the 

 origin of the anterior roots. The means of research at present 

 at our command have not indeed permitted a nerve fibre be- 

 longing to the anterior root to be followed directly to a nerve 

 cell ; but transverse sections of the spinal cord treated with 

 chloride of potassium and gold, and longitudinal sections 



