What happened to Lazarus?

Lazarus got stuck in quicksand.... he was sucked in and died.

"Ivan," he said to Rainsford, "will supply you with hunting clothes, food, a knife. I suggest you wear moccasins; they leave a poorer trail. I suggest, too, that you avoid the big swamp in the southeast corner of the island. We call it Death Swamp. There's quicksand there. One foolish fellow tried it. The deplorable part of it was that Lazarus followed him. You can imagine my feelings, Mr. Rainsford. I loved Lazarus; he was the finest hound in my pack.