NERVE AS MODEL TEMPERATURE END ORGAN

The main stem of the sciatic nerve of deeerebrate or chloralosed cats was locally cooled or warmed by a thermode and the discharge recorded from one of the roots, generally from the sensory LT. The thermode was a small, lacquered metal container with a cross-section like a shallow U forming a groove for the nerve and dosed from above by a thin metal lid. The length of the canal for the nerve was 2 cm. The temperature of the thermode was regulated with running water and measured by a thermocouple placed at the bottom of the groove for the nerve and connected to a galvanometer. By pressing a button the experimenter marked on the film the mo- ment when, during warming or cooling, the galvanometer spot passed a scale unit. This meant that every fourth degree of change was recorded. The condenser-coupled amplifier for the massed discharge from the root was led to a loudspeaker as well as to a diode rectifier for integrating the total effect. TMs way of measuring irregular spike activity in a large number of fibres seems more satisfactory than trying to count the individual spikes. To begin with, the experiments were 257