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 gi-oups 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 wdiich 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). 

 Fifi. 15. -'Sympathetic' Gan- The cclls are pcar-sliapcd and the 



glioii-cell of a Frog, very higlily . n ^ r ^ 



magnified ; according to Beale. naiTOW extremity 01 Cacll 01 them 



Keduced and adapted from one of j^ continued iuto a prOCCSS which 

 his figin-es. a a, straight nhre ; o, -t 



coiled fibre ; c, smaller one joining in tum bcCOmCS COlltinUOUS witll 



a dark-bordered fibre, whilst one 

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



