“Sometimes he pursued the call into the forest, looking for it as though it were a tangible thing, barking softly or defiantly... Irresistible impulses seized him. he would be lying in camp, dozing lazily in the heat of the day, when suddenly his head would lift and his ears cock up, intent and listening, and he would spring on his feet and dash away, and on and on, for hours, though the forest aisles.”