ME. G. J. EOMANES ON THE LOCOMOTOE SYSTEM OF MEDUSAE. 
723 
(/) Submitting a contractile strip to slight strains has also the effect of retarding the 
rate of the waves while they pass through the portions of the strip which have been sub- 
mitted to strain. The method of straining which I adopted was to pass my finger below 
the strip, and then, by raising my hand, to bring a portion of the strip slightly above the 
level of the water. The irritable, or contractile, surface was kept uppermost, and there- 
fore suffered a gentle strain ; for the weight of the tissue on either side of the finger 
made the upper surface somewhat convex. By passing the finger all the way along the 
strip in this way, the latter might be gently strained throughout its entire length, the 
degree of straining being determined by the height out of the water to which the tissue 
was raised. Of course if the strip is too greatly strained, the contractile waves become 
blocked altogether, as described in my last paper ; but shortly before this degree of 
straining was reached, I could generally observe that the rate of the waves was dimi- 
nished. To give one instance, a contractile strip measuring 22 inches had the rate 
of its waves taken before and after straining of the kind described. The result was as 
follows : — 
Fig. 14. 
Before straining 
After straining 
One second. . . . 
Immediately after severe handling of this kind, the retardation of contractile waves 
is sometimes even more marked than here represented; but I think this may be partly 
due to shock ; for on giving the tissue a little while to recover, the rate of the waves 
becomes slightly increased. 
(g) Anaesthetics likewise have the effect of slowing the rate of contractile waves 
before blocking them. Taking, for instance, the case of chloroform, a narrow spiral 
strip 28 inches long was immersed in sea-water containing a large dose of the anaesthetic ; 
the observations being taken at six seconds’ intervals, the following were the results : — 
5 i 
MDCCCLXXYII. 
