80 The Physiology of Sense Organs 



peripherally towards the soma as well as towards the central 

 nervous system. The sequential advance of the action potential 

 recorded at loci between this point and the soma was found to be 

 consistent with this view. 



Fig. 35. Relative times of occurrence of different parts of 

 the action potential wave-form as recorded extracellularly 

 from different regions of a crayfish stretch receptor neuron. 

 The impulse appears first as a diphasic transient at B, a point 

 about 500 microns central to the cell body. (From Edwards 

 and Ottoson,^^ Fig. i.) 



Investigations of multichanneled central neurons in a variety 

 of preparations have resulted in essentially similar findings. The 

 soma and dendritic regions of the cell are intimately involved in 

 the generation of graded, non-regenerative potential changes 

 under the influence of synaptic transmitter substances, and they 

 may even be secondarily invaded by antidromically propagating 



