EFFECTS OF STRETCH ON MUSCLE RESPONSES IN 
THE EARTHWORM 
(. HBLODRILUS CALIGINOSUS ) 
B. M. HARRISON 
Much investigation has been done on the physiology of the 
muscles of the vertebrates as compared with that of the inverte- 
brates. Buddington 1 (’02) brings together the bibliography bear- 
ing on this problem, and shows that with increasing temperature 
Lumbricus muscle shows little constancy in changes of tone be- 
low 15° C and the first uniform result is a gradual loss of tone 
beginning at 20° C; rapid loss of tone occurring between 30° 
and 40° ; an improvement from 42° to about 55° when rapid 
relaxation sets in, this changing to final heat rigor at about 65°. 
Eddy and Downs 2 (’21) showed that the gastrocnemius muscle 
of the frog when stretched by a weight of 100 grams for one- 
half to three hours can be completely fatigued in 85.98 per cent 
of the time required in the case of an unstretched muscle, when 
both were stimulated by the same strength induced current. 
Harrison and Baldwin 3 (’21) obtained definite qualitative dif- 
ferences in responses in earthworm muscle in concentrations of 
alcohols, ranging in ethyl alcohol from 40 to 1.56 vols per cent, 
and in propyl alcohol from 10 to 0.5 per cent. In general, the 
higher concentrations are toxic, the lower have no noticeable 
effect, while between the two extremes are concentrations of de- 
cided sensitization. 
APPARATUS AND METHOD 
The apparatus used in this series of experiments was the same 
as described in a previous paper by Harrison and Baldwin 3 (’21). 
A more detailed description of a part of the apparatus is given by 
Harrison 4 (’23). A tetanizing electric current was employed for 
stimulating, strengths of 6 and 8 volts were used as subsequently 
described. The secondary coil of the inductoipum was set at 4J4 
centimeters from the primary, where it was maintained throughout 
the entire series of experiments. The kymograph was adjusted 
to make one revolution in one hour. The inductorium was ad- 
justed so as to give thirty-eight to forty make and break stimuli 
