The Apparatus

The nerve bath consists of a perspex, lidded box with inserts for five electrodes. The electrodes are plastic coated wire enclosed in perspex tubing and can be moved relative to each other.

Two of the electrodes are used for stimulating the preparation and must be connected to the two leads from the stimulator. Ensure that the negative lead is the inner lead.

The two other electrodes serve to record the activity of the nerve and should be connected to the input leads of the amplifier.

The last electrode serves as an earth, and is connected to the earth lead. This electrode must be placed between stimulating and recording electrodes and serves to prevent much of the stimulating current being picked up by the recording electrodes. The small amount of current which does pass the earth electrode produces the stimulus artefact.

The electrodes are positioned as shown below. The sciatic nerve is laid carefully across the five electrodes and a little frog Ringer solution poured into the bottom of the bath (note the nerve should not be immersed). At room temperature, with the lid in place, this ensures that a humid atmosphere is maintained within the organ bath.