The Control of Impulse Frequency 57 



and the stimulus source, the response to prolonged deformations 

 was considerably shorter than when they were applied directly 

 to the nerve-ending itself. It therefore seems reasonable to 

 conclude that a major factor in the adaptation process of the 

 Pacinian corpuscle is the mechanical filtering characteristic of the*^ 



J J\ T\ 



A- 



i^v. 



ij\m ■!■ t'^Jw 



J 



Fig. 24. Receptor potentials (upper traces, a-c) obtained in 

 response to mechanical pulses of varying duration (monitored 

 on bottom trace) from a Pacinian corpuscle. The responses in 

 rows a and b were obtained after the capsule had been dissected 

 away from the nerve-ending. The response in c was obtained 

 from the intact receptor. Calibration pulses: 10 msec, and 

 50 fxV. (From Loewenstein and Mendelson,'* Fig. 2.) 



capsule, which couples the stimulus to the sensory cell. This 

 latter principle is of some importance, for, regardless of the rapid 

 accommodation which characterizes the sensory axon, a large part 

 of the initial decline in the ability of the receptor to respond 

 repetitively clearly occurs as a result of the effective removal of the 

 stimulus at the level of mechano-electric conversion, even though 

 the outer layers of the capsule itself may still be exposed to it. 



Some additional support for the role of mechanical factors in 

 adaptation comes from work on the mammalian muscle spindle."' 

 S.O.— E 



