FUNCTIONS OF THE NERVE-CELL 



353 



of blood-supply the ganglion-cells died. But Steinach found that nerve 

 impulses were still conducted perfectly well through the ganglion at a 

 time when microscopic examination showed a complete atrophy of 

 all cells. It is therefore only in virtue of the fact that the nerve-cell is 

 the seat of the nucleus, and therefore of the assimilative functions of 

 the neuron, that any pre-eminent importance can be ascribed to it in 

 the building up of a reactive nervous system. 



Prominent among the functions with which the nerve-cell has 

 been endowed is that of automaticity of action in the absence of 





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 \ ( 



= 



;l luS 



Fia. 153. Diagrammatic representation of the brain of Carcinus to show 

 the parts involved in Bethe's experiment. The dotted line x shows 

 the incision employed to isolate the neuropilem of the ganglion of the 

 second tentacle. 



stimulus other than that supplied by its own metabolism or by the 

 fluids which bathe it. A priori there is no reason to deny to the neuron 

 a property which is possessed by other cells of the body, such as the 

 muscular cells of the heart, and which is a fundamental quality cf 

 undifferentiated protoplasm. The purpose, however, for which these 

 cells have been evolved and differentiated is that of reaction, of 

 adapting the organism to changes in its environment, and it is doubtful 

 whether, in this differentiation, it has retained any automatic 

 properties whatsoever. In the absence of any afferent impulse the 

 whole central nervous system w T ould probably be inert. In a frog- 

 retaining only the spinal cord Hering divided all the posterior roots. 

 The frog remained flaccid and motionless. Injection of strychnine 

 was powerless to evoke the usual tetanic spasms. In such a strych- 



23 



