Electricial Activity in a Slug Ganglion in Relation to the Concentration of Locke Solution

Abstract

1. A method is described by which the electrical activity of single units in the isolated pedal ganglia of the slug Agriolimax reticulatus can be studied quantitatively for many hours. When tungsten microelectrodes were used the results were more simple and less variable than those obtained using external silver-silver chloride electrodes. 2. The activity studied consisted of potentials of characteristic size and shape. Their frequency was usually about 30/min. No correlation was observed between these and any rhythmic activity of the animal. 3. The blood of the slug shows considerable variation in its water-content, ranging from a concentration equivalent to that of a 1.4 Locke solution in dehydrated animals to one equivalent to 0-45 Locke in hydrated animals. Animals taken straight from a garden in the evening had a body fluid equivalent to 0.7 Locke. 4. The ‘spontaneous’ activity of the isolated pedal ganglia was greatly affected by a change in the concentration of the bathing solution. Concentration of the medium decreased the activity and dilution increased the activity. This effect appears to be due to the change in osmotic pressure rather than a change in the concentration of individual ions. The possible significance of these changes in the life of the animal is discussed.