But even as he permitted these thoughts partially to reassure him, there came strongly to his nostrils a scent that always caused the short hairs upon his head to rise, not in fear but in natural reaction to the presence of an hereditary enemy. It was not an odor that he had ever smelled before. It was not the scent spoor of Numa the lion, nor Sheeta the leopard, but it was the scent spoor of some sort of great cat. And now he could hear its almost silent approach through the underbrush and he knew that it was coming down toward the trail, lured either by knowledge of his presence or by that of the beast whose approach Tarzan had been awaiting. It was the latter who came first into view--a great ox-like animal with wide-spread horns and shaggy coat--a huge bull that advanced several yards along the trail after Tarzan discovered it before it saw the ape-man dangling in front of it. It was the thag of Pellucidar, the Bos Primigenus of the paleontologist of the outer crust, a long extinct progenitor of the bovine races of our own world. For a moment it stood eyeing the man dangling in its path. Tarzan remained very quiet. He did not wish to frighten it away for he realized that one of them must be the prey of the carnivore sneaking upon them, but if he expected the thag to be frightened he soon realized his error in judgment for, uttering low grumblings, the great bull pawed the earth with a front foot, and then, lowering his massive horns, gored it angrily, and the ape-man knew that he was working his short temper up to charging pitch; nor did it seem that this was to take long for already he was advancing menacingly to the accompaniment of thunderous bellowing. His tail was up and his head down as he broke into the trot that preluded the charge. The ape-man realized that if he was ever struck by those massive horns or that heavy head, his skull would be crushed like an eggshell. The dizzy spinning that had been caused by the first stretching of the rawhide to his weight had lessened to a gentle turning motion, so that sometimes he faced the thag and sometimes in the opposite direction. The utter helplessness of his position galled the ape-man and gave him more concern than any consideration of impending death. From childhood he had walked hand in hand with the Grim Reaper and he had looked upon death in so many forms that it held no terror for him. He knew that it was the final experience of all created things, that it must as inevitably come to him as to others and while he loved life and did not wish to die, its mere approach induced within him no futile hysteria. But to die without a chance to fight for life was not such an end as Tarzan of the Apes would have chosen. And now, as his body slowly revolved and his eyes were turned away from the charging thag, his heart sank at the thought that he was not even to be vouchsafed the meager satisfaction of meeting death face to face.