Abstract
The experiments on which the present observations are based are a continuation of a previous investigation (Lindeman 1 ) on the effect of various ions upon the heart rhythm of the crayfish Cambarus
clarkii. However, instead of employing the normal blood ions, a group of closely allied ions, found in the same periodic classification of metals were employed, namely, Li, NH4 Sr and Ba.
The species of crayfish used was that of Cambarus clarkii. The same general technique was employed for obtaining graphic records as described in the above investigation. A normal perfusing solution containing 1% NaCl +0.028% KCI +0.024% CaCL2 was employed as a control bath and as a basis for observing the effect of the solutions containing different ionic concentrations. The author has demonstrated in a previous paper that a 1% NaCl solution produces for a time a rapid decrease in tone and an increase in rate and amplitude of the beats. With continuous application, arrest is produced in about 30 minutes.
1% LiCl causes an increase in tone, followed shortly by arrest. However, upon the application of a 0.5% LiCl solution to the heart of a crayfish which has been beating normally with a normal perfusing solution, a decrease in tone immediately follows, coupled with an increase in rate and amplitude. With continued perfusing the rate and amplitude slowly decrease, with ultimate arrest in about 25 minutes. Because of the apparent similarity of 0.5% LiCl and the 1% NaCl in their action upon the heart rhythm of the crayfish, an attempt was made to replace part of the NaCl in the normal perfusing solution with LiCl.
If the intact heart is perfused with a solution containing 0.3% LiCl + 0.7% NaCl + 0.028 KCl + 0.024% CaCl2, it will continue to beat normally for several hours.
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