Sensory Cell Function and Architecture 83 



receptor. Invasion of the soma by the spikes occurred in all 

 instances, except one in which, perhaps due to refractoriness of 

 the excitable membrane, only the electiotronic potential from a 

 distantly-blocked impulse was seen. After these records had been 



.AM. 



VV- 



^1 

 gl 



Smtte. 



Fig. 36. Intracellular electrical records obtained from the 

 soma of a crustacean bipolar mechanosensory neuron. The 

 cell was in an unhealthy condition, and orthodromic impulses 

 initiated by mechanical stimuli (A) had rather unusual wave- 

 forms, indicating a delayed invasion of the soma (and in one 

 case, non-invasion) by the centrally propagating impulses. 

 Similar waveforms were obtained following electrical 

 stimulation of the distal process of the cell (B), (C), The 

 record in D is of an antidromic impulse. (From Mellon 

 and Kennedy," Fig. 7.) 



photographed, several brief electrical shocks were delivered to the 

 distal process. These stimuli initiated impulses which propagated 

 towards the soma. The responses obtained in two of these 

 instances can be seen in figure 36 B and C. The waveforms of 

 the two closely resemble those obtained following mechanical 

 stimulation and are quite unlike that of an invading antidromic 

 impulse (figure 36D). The results strongly support the concept 

 of a distal locus for the site of initiation of propagated impulses 

 in these cells. Quite recently, results similar to these have been 



