The circulatory physiology of Helix pomatia. I. Observations on the mechanism by which Helix emerges from its shell and on the effects of body movement on cardiac function.

Previously reported work on the cardiac physiology of Helix pomatia has been concerned with partly dissected animals or isolated hearts. The present work has been concerned with observing the living animal carrying out normal movements under the minimal amount of experimental interference. The way in which the animal emerges from its shell has also been investigated. During the breathing cycle the muscular floor of the mantle cavity (roof of cephalopedal haemocoel) is depressed, thereby increasing the volume of the cavity, while the pneumostome opens and air enters. The pneumostome then closes and the mantlecavity floor rises, reducing the volume of the cavity (Meisenheimer, 1912). These movements are accompanied by characteristic changes in heart rate which have been shown to be under nervous control in the partially dissected animal (Rywosch, 1905; Carlson, 1905; Zubkov, 1935; Jullien & Ripplinger, 1953; Jullien et al i960; Meng, 1958). In the present experiments the cardiac nerve has been severed, leaving the animal otherwise intact so that the hydrodynamic effects on heart rate could be investigated. The course and structure of the anterior (cephalic) aorta has been investigated in Helix pomatia, Helix aspersa, Arion ater and Archachatina purpurea.