Two important events in Chapter 3

From the text:

1) But when Buck finished his ration and returned, he found his nest occupied. A warning snarl told him that the trespasser was Spitz. Till now Buck had avoided trouble with his enemy, but this was too much. The beast in him roared. He sprang upon Spitz with a fury which surprised them both, and Spitz particularly, for his whole experience with Buck had gone to teach him that his rival was an unusually timid dog, who managed to hold his own only because of his great weight and size.

2) In the meantime the astonished team-dogs had burst out of their nests only to be set upon by the fierce invaders. Never had Buck seen such dogs. It seemed as though their bones would burst through their skins. They were mere skeletons, draped loosely in draggled hides, with blazing eyes and slavered fangs. But the hunger-madness made them terrifying, irresistible. There was no opposing them.