In this passage, Travis numbs himself in order to carry out the painful responsibility of putting down Old Yeller before he can spread the hydrophobia that the wolf almost certainly infected him with. Thus far, Travis has had conflicting ideas about masculinity, bravery, and responsibility. Here, he decides that being a man and taking responsibility means shutting himself off from his emotions—the only way to get through this disturbing act is to detach completely from what he’s doing.