Influence of hexane solubles in tobacco on a polycyclic fraction of cigarette smoke

Six rats, working in a 2 degrees C ambient temperature, were trained to depress a lever to receive a brief period of heat. Four rats were then moved into the 2 degrees C environment to live, while the others continued to live at room temperature. Living at a temperature of 2 degrees C increased the number of heat presentations the animals delivered to themselves.