In chapter four of The Call of the Wild, by Jack London, Buck has persisted and finally become the leader of the team. Dave is one of the dogs who does not mind who the leader is; he knows his "business [is] to toil, and toil mightily, in the traces."
The mail runs these make are quite hard, for the dogs are "short of weight" and have been pulling a heavy load; they should have been allowed to rest for at least a week, perhaps even ten days. Instead they are on the trail again in two days. All of the dogs are struggling, but "it was Dave who suffered most of all. Something had gone wrong with him."
Dave is depressed and irritable, and when he is released from his traces he literally drops where he stands and both sleeps and eats there; he does not get up again until it is time to be re-harnessed in the morning.
Sometimes, in the traces, when jerked by a sudden stoppage of the sled, or by straining to start it, he would cry out with pain.
Though the men examine Dave, they do not discover anything obvious, One night they all get together and drag Dave closer to the fire and Dave
was pressed and prodded till he cried out many times. Something was wrong inside, but they could locate no broken bones, could not make it out.
When the men try to give Dave a rest by having him run behind the sled rather than help pull the load, the dog resents it and growls until he is given his place back. When it is clear that Dave is not going to make it, the driver reads the sorrow in Dave's eyes and lets the creature save his pride by keeping him connected to the harness.
For the pride of the trace and the trail was his, and, sick unto death, he could not bear that another dog should do his work.
Dave struggles to stay connected to the team because he wants to do his job until he can do it no longer.