ABSTRACT
As far as they have been studied the muscles of the body wall of annelids have been found to be sensitive to acetylcholine. The dorsal musculature of Hirudo medicinalis L. responds by contraction to a low concentration of the drug (Minz, 1932); among the chaetopods a similar effect has been shown with the body wall of Lumbricus terrestris L., Arenicola marina L. (Wu, 1939) and Branchiomma vesiculosum (Montagu) (Nicol, 1952). In all cases the threshold of response is at dilutions of 10−4 to 10−6. No such responses have generally been found with the skeletal muscles of the Crustacea. Bacq (1935) reports that the muscles of Carcinus maenas (Pennant) and Lepas anatifera L. do not respond to acetylcholine at a concentration of 10-4; du Buy (1935) was unable to elicit any response to crystals of the drug from the muscles of Cambarus sp.; Katz (1936) found no response from the muscles of Carcinus maenas to acetylcholine at a concentration of 10-5, but observed a ‘moderate short contracture’ to a concentration of 10-4;* Ellis, Thienes & Wiersma (1942) detected no response from the claw muscles of Cambarus clarkii Girard even at concentrations of 10-1.
Katz has given reasons for the belief that this response was due to a direct action of the drug upon the motor nerve (Bacq, 1937).
