SMOOTH MUSCLE RESPONSES 
181 
back of the clitellum. The frogs upon which a large series of ex- 
periments were made were obtained from The Anglers Company, 
Chicago, and were placed in a tank with water where the temper- 
ature was rather constant, varying only slightly from room tem- 
perature (around 70° F.). At the time of experiment they were 
pithed and the spinal chord destroyed, a portion of the region de- 
sired removed and placed usually in 0.7 per cent salt solution. 
Great care was observed in removal of the part desired so as to 
standardize ^s far as possible any differences in response which 
might conceivably be attributed to differences in extent and mor- 
phological position of the part. In the removal of the esophagus, 
the cutting was so done as to obtain a portion about a centimeter in 
length. The first incision was made just anterior to the branch 
of the artery supplying the posterior portion, and another cut was 
made just posterior to the point of immergence of the tube into the 
abdominal cavity. The same care was exercised in removing 
portions of the stomach, since portions close to either end ex- 
hibited rhythmical responses probably due to their respective 
sphincter muscles. Usually rings of about one cm. in length 
from the central area were used, although mention of the be- 
havior of other areas will be made later. 
When portions of the body wall of the earthworm were used, 
the procedure in preparation was as follows: Specimens of 
various species were obtained on the campus and brought into 
and kept in the laboratory in a jar of moist earth, the room being 
kept at about 70° F. A specimen at the proper time Was removed 
from the jar, washed in tap water to remove dirt and grit and 
placed on a moistened cork pad. In a short time it was quiet 
enough to count under a dissecting lens ten somites which in all 
cases constituted the desired ring of tissue. The first ten somites 
were taken just in back of the clitellum, and then successive rings 
of ten were cut as needed subsequently, the posterior portion of 
the worm being placed in the meantime in tap water just suffi- 
cient to keep it moist, but not submerge it. 
A technique of mounting the tissues in question was developed 
which was found to be very important to the success of the result- 
ing experimentation, and a word needs to be said just here. Two 
equilateral triangles (1 cm. a side) of fine (about No. 24) copper 
wire, were made in such a way as to form a sort of safety-pin, 
with a hook-like clasp at one end. By running the free end of 
each triangle through the ring of tissue and clasping, the triangles 
