300 C. EYZAGUIRRE 



dromic impulse, but in this case the first antidromically occurring impulse does 

 not have the initial pre-potential phase (Fig. 1 1). 



The absence of pre-potentials preceding each member of such group 

 discharges and the high frequencies (up to 500/sec) clearly distinguish this 

 type of activity from the usual stretch-evoked impulse. Moreover, the fact 

 that stretch actually reduces the grouped discharge or abolishes it indicates 

 that the impulses are not set up by the normal generator mechanism. 



Fig. 11. Grouped discharges' from a slow^cell. a. Intracellular lead from cell 

 soma of a lightly extended cell. No antidromic stimulation. The complex potential 

 was accompanied by three sensory axon impulses (not shown). A pre-potential 

 precedes the first large deflection (O). b. Same cell with simultaneous extra- 

 cellular axon impulses on the lower beam. First deflection set up by antidromic 

 stimulus (a). Components 1 and 2 were always associated with afferent impulses 

 recorded in the axon. (From Eyzaguirre and Kuffler, J. Gen. Physiol. 39 : 



121-153, 1955b.) 



Eyzaguirre and Kulfler (1955b) interpreted this observation in the following 

 way: The first fully grown impulse in the cell soma resuhing from antidromic 

 invasion or from orthodromic excitation invades one or more dendrites with 

 some delay. During this delay period the soma impulse reaches its recovery 

 phase; when the dendrite impulses occur they propagate towards the soma 

 as well as toward the terminal region. Since the soma is still refractory; for 

 instance, 0-5 to 2-0 msec after the spike peak, only a local response could be 

 added. This local response may be too small and may die out (hke the soma 

 deflections not correlated with afferent activity) or it may spread into the 



