The Call of The Wild by Jack London Chapter 2 Page 14

Dave was wheeler or sled dog, pulling in front of him was Buck, then came Sol-leks; the rest of the team was strung out ahead, single file, to the leader, which position was filled by Spitz.

Buck had been purposely placed between Dave and Sol-leks so that he might receive instruction. Apt scholar that he was, they were equally apt teachers, never allowing him to linger long in error, and enforcing their teaching with their sharp teeth. Dave was fair and very wise. He never nipped Buck without cause, and he never failed to nip him when he stood in need of it. As Fran�ois’s whip backed him up, Buck found it to be cheaper to mend his ways than to retaliate. Once, during a brief halt, when he got tangled in the traces and delayed the start, both Dave and Sol-leks flew at him and administered a sound trouncing.