PHYSIOLOGY: J. F. McCLENDON 
703 
THE EFFECT OF STRETCHING ON THE RATE OF CONDUCTION IN 
THE NEURO-MUSCULAR NETWORK IN CASSIOPEA 
By J. F. McClendon 
DEPARTMENT OF PHYSIOLOGY. UNIVERSITY OF MINNESOTA AND TORTUGAS LABORATORY, 
CARNEGIE INSTITUTION OF WASHINGTON 
Communicated by A. G. Mayer, September 21. 1917 
It was observed by Carlson {Amer. J. Physiol., 27, 1911, 323) that 
stretching the nerve of the slug has no effect on the rate of the nerve 
impulse. This does not support Bethe's hypothesis that the impulse 
passes over solid neuro-fibrillae which are zig-zagged in the relaxed 
nerve and straightened out in the stretched nerve. Conditions are not 
so simple in the nervous network of the sub-umbrella of Cassiopea, but 
the rate may be more accurately determined. The stretching may 
increase the original length 84%. 
A ring or belt of umbrella tissue was placed in a frame by means of 
which the circumference could be stretched and at the same time its 
length measured. The apparatus was immersed in sea-water kept at 
30°. A neuro-muscular wave was started in the ring in such a manner 
that it traveled continuously around the ring and its speed measured 
by noting the time at which the muscular contraction wave passed a 
certain point. The time required for the wave to pass 100 times around 
the ring was recorded with a stop-watch. An example of one of the 
experiments is as follows: 
Length of circumference, mm. 286 306 326 346 366 386 406 426 446 466 486 506 526 
Rate (mm. per second) 376 390 399 410 414 407 403 391 377 368 360 352 342 
It may be noted that the rate changed 17% while the length increased 
84%, in other words the rate is relatively constant. An uncertainty of 
rate of 1-5%, due to hysteresis, could not be analyzed with certainty 
owing to the fact that the course of the neuraxones is zig-zagged and 
interrupted by synapses, but some speculation on this phenomenon will 
be published elsewhere. The purpose of this abstract is to point out 
that the experiments on Cassiopea tend to support Carlson's conclusion 
that stretching the nerve does not change the rate, and that the con- 
ducting substance, itself, can be stretched and relaxed. 
