46 



THE STRUCTURE OF 



cells of a motor group by one or other of these modes 

 though in regard to this point we have even less certain 

 knowledge than concerning the last. Of the existence 

 of such connecting or ' commissural ' fibres which are 

 either short or long according to the proximity or re- 

 moteness of the two groups of 

 cells there can be no doubt. 

 Uncertainty exists, however, with 

 regard to the precise mode of their 

 connection with the sensory nerve 

 cells on the one side and the 

 motor on the other whether at 

 either extremity they are continu- 

 ous with undivided cell-processes, 

 or break up and inosculate with 

 ramifying cell-processes. 



More room for doubt, therefore, 

 exists in regard to the precise 

 modes in which stimulus waves 

 traverse nerve centres, than con- 

 cerning the manner in which they 

 impinge upon or depart there- 

 from. 



6. In the ' sympathetic ' or vis- 

 ceral ganglia of the Frog and other 

 animals another kind of relation 

 between fibres and cells has been 

 shown to exist (Lionel Beale). 

 FIG. 15. -'Sympathetic- Gan- The ceUs are pear-shaped and the 



ghon-cell of a Frog, very highly * x 



according to Beaie. narrow extremity of each of them 



coiled fibre ; c, smaller one joining in turn becomes COlltinUOUS with 



a dark-bordered fibre, whilst one 

 or, it may be, two or more smaller fibres seem to arise from 



