4 Foster, Physical Basis of Psychical Events. 



unbranched course, it may be for a short, it may be for an 

 exceedingly long distance, eventually ends in a terminal 

 branching arborisation. Such are the main features of a 

 typical nerve cell or neurone, a nucleated cell body giving 

 off on the one hand branched dendrites, and on the other 

 hand an undivided axon. There are, I need hardly say, 

 variations from the type, but on these I need not now 

 dwell. 



The nerve cell or neurone is the unit of the nervous 

 system in the sense that the whole system is made up of 

 neurones, linked together in a special way, and surrounded 

 by or embedded in aground work, consisting of connective 

 tissue carrying blood vessels and lymphatics, and of a 

 special tissue called neuroglia, which ground work supports 

 and nourishes the active real nervous tissue and at the 

 same time serves to isolate each nervous element from its 

 neighbours. 



The mode of linkage deserves attention. In so many 

 cases has it been observed that the terminals of an axon, 

 either of the stem or of the collaterals, by means of 

 branching or arborisation, more or less complex, impinge 

 upon or surround or intertwine with the dendrites or some 

 part of the cell not itself an axon, that this may be con- 

 sidered as the mode in which the cells are connected 

 together. Axon does not link with axon, or dendrite with 

 dendrite, the linkage is that of axon with dendrite. 

 Further, in so many cases the connection has been found 

 to be one not of fusion but of contact, there being a break 

 of continuity at the linkage between the material of the 

 axon and that of the dendrite, that this, too, has been 

 assumed to be an essential feature of the linkage. This 

 assumption, however, must be received with caution ; 

 indeed, it is maintained by some observers that in certain 

 cases distinct fusion may be observed. But it may be 

 argued that these cases are only apparent exceptions, the 



