Fish, The Nerve Cell as a Unit. 109 



idea has been advanced that even in the adult state the neurocyte 

 has not completely lost its power of amoeboid movement, but 

 that this property is still retained at the terminals of its appen- 

 dages. This view is not accepted by KoUiker, nor entirely by 

 Cajal, who thinks that the neuroglia cells are more mobile than 

 the nerve cells. 



The experiments upon the activity and fatigue of the nerve 

 cell indicate that a change of volume may occur, a turgescence 

 as a result of activity, and a shrinkage when carried to the ex- 

 tent of fatigue. Situated in the lymph spaces and constantly 

 bathed with the lymph for nutritive purposes, we may expect to 

 find certain osmotic processes going on between the contents of 

 the cell and its surrounding medium and that these processes 

 may be influenced by the activity of the cell and that certain of 

 them may occur coincidently with the transmission or origina- 

 tion of the impulse in the cell. 



Along the dendrite, and especially well pronounced in the 

 cortical cells, are slight lateral spurs known as gemmulas. The 

 condition of these, as well as certain irregularities in the form 

 of the dendrites, have been noted by Berkley and others as the 

 result of pathological causes. Berkley has shown that in cer- 

 tain diseased conditions gemmulae have been missing. He be- 

 lieves that the cell and its dendrites has a delicate limiting mem- 

 brane through which the gemmulas protrude, as naked bits of 

 protoplasm, coming into contact with similar uncovered masses 

 of protoplasm from the neurite or its collaterals, or in contact 

 with the gemmulae of other dendrites and that at these points 

 the impulses are transferred. Any destruction or abnormality 

 of these gemmulae would of course, interfere more or less seri- 

 ously, with the normal conveyance of the impulse. 



The transference of nervous impulses from one element to 

 another through contact, due to amoeboid movement, would be 

 of material importance in the explanation of the phenomena of 

 sleep, intellectual processes, and pathological conditions. Before 

 pathology has spoken its final word we may hope to know more 

 of the remarkable chemical complexity of nervous tissue, com- 

 posed, as it is said, of some three hundred or more different ele- 



