Effects of Drugs on the Hearts of Arenicola and Lumbricus

The action of several drugs upon the hearts and pulsating dorsal vessel of A renicola cristata and Lumbricus terrestris was observed by counting the beats during in situ perfusion. The counting was sometimes facilitated by tapping the rhythm of several vessels on keys connected to signal magnets recording on a kymograph. Actual kymographic tracings were obtained of the beating Arenicola hearts both in situ and in perfusion chambers. Light, glass-tipped wire levers were used with magnification ratios of from 3.5 to 11.5 times. Tensions on the isolated hearts were from 65 to 100 mgm. Careful adjustment of tension by means of small wire riders was necessary, since with these, as with all other invertebrate hearts, the strength and frequency of beat increases up to a maximum and then declines with increasing tension and rate of flow. In no cases were the vessels cannulated; solutions bathed them from outside. Both Arenicola and Lumbricus were first anesthetized with saturated chloretone solution. Then the hearts were exposed, dorsal body wall pinned back to paraffin blocks, and time allowed for complete recovery during continual flow of saline. Recovery required between 30 and 6o minutes in Arenicola, a little less in Lumbricus. Before removal of the Arenicola hearts the ventral vessel was ligated with the loop which served for attachment in the chamber, the heart and part of the lateral gastric vessel were removed, and either a tiny glass hook inserted in the dorsal part of the heart or a ligature placed around the lateral esophageal vessel for connection to a lever. Sea water proved an excellent physiological saline for Arenicola. In the earthworm both frog Ringer and Bruna's fluid (Jordan and van der Feen, 1930) proved very unsatisfactory. Using Maluf's (1940) analyses and freezing-point measurements of coelomic fluid as a basis and varying the Ca/K ratios over a wide range, we prepared an earthworm saline, which maintained a fairly steady beat for the duration of the experiment, which was 3-4 hours. We have not attempted to keep hearts going for longer periods, but in one a good beat was noticed after 12 hours in the flowing saline.