Fish, The Nerve Cell as a Unit 1(31 



to confirm it, that there is complete morphological indepen- 

 dence of the nerve elements, with perhaps certain exceptions, in 

 rare cases, where a direct anastomosis of one nerve cell with 

 another has been described, as in the battery of the torpedo and 

 also in certain of the sense organs, as noted by Dogiel, Ayers, 

 Masius and others. This morphological isolation of the ele- 

 ments does not preclude the idea of physiological continuity 

 which must of necessity exist. 



This isolation of elements has led to the production of the 

 term neuron (Waldyer '91), neurone (Van Gehuchten '93), 

 neurocyte (Fish '94, after an unknown French writer), neura 

 (Rauber '94) and neure (Baker '96), to signify the nerve unit, 

 including the cell body with all its appendages. The term 

 neurocyte has been suggested in this connection because its lit- 

 eral meaning is a nerve cell and includes not merely the cell 

 body, which from custom we regard as the equivalent of a nerve 

 cell, but all of its appendages as well, just as in speaking of the 

 leucocyte, we include the various extensions from the cell mass. 

 The analogy may be carried still farther for under certain special 

 conditions we may conceive that the pseudopodia of the leuco- 

 cyte may be considerably extended and attenuated and from the 

 juxtaposition of numerous other elements lose, or partially lose, 

 their powers of retraction and movement ; under such condi- 

 tions we may consider the neurocyte comparable with the leuco- 

 cyte so far as form is concerned. 



The appendages of the cells, with perhaps the exception of 

 those of the spinal ganglia, appear to fall naturally into two 

 categories ; those which collect or convey the impulse to the 

 cell, cellipetal processes or dendrites, and those which discharge 

 or carry impulses away from the cell, the cellifugal processes or 

 neurites (axis-cylinders). 



Along with our increasing knowledge of the form of neuro- 

 cytes there have been contributed new facts bearing upon their 

 activity. For our purpose, we may consider the neurocyte as 

 made up of a mass of granular protoplasm, with more or less 

 branching appendages, containing a large nucleus of a reticu- 

 lated character enclosing, usually, a prominent nucleolus. We 



