In The Call of the Wild, what does "If I don’t get the hydrophoby" mean?
As the above answer states, 'hydrophoby', or hydrophobia, refers to rabies, the often-fatal disease which humans can contract from dogs and other animals, usually wild animals. The bitten man isn't allowed to finish his sentence: he says, 'If I don't get the hydrophoby - ' but is interrupted by the saloonkeeper who jokes that, if he doesn't get hydrophobia, it would only be he was 'born to hang'.
Rabies is generally associated with wild, or stray dogs. Buck, of course, was not wild to begin with, but rather appeared as a thoroughly domesticated house pet in in the 'lazy, sun-kissed' home of Judge Miller in California. However, by this stage in the novel, those old domestic docile traits are beginning to slip rapidly away from him, as he is chained, caged and brutalized by his kidnappers. At one point he appears as a 'red-eyed devil', but he is ultimately brought down by one experienced doghandler, or dog-breaker who finally knocks him out with a club. At this point he realizes that it's better to co-operate with these men, rather than try to fight them all the time, and quickly adjusts to the rough life in the north as a sled-dog.
In the course of the novel, though, Buck finally leaves behind all human contact and ends up reverting entirely to the wild, when he runs off to join a pack of wolves - wolves being the common ancestors of modern dogs, as the narrative frequently reminds us. Buck's reversion is thus seen as a return to his true, hereditary nature.
"Hydrophoby" is a folksy pronunciation of hydrophobia, better known today as rabies.
Rabies was once called hydrophobia because an early symptom of the fatal disease is difficulty in swallowing. When offered a drink of water, victims would often refuse to drink, showing what appeared to be a fear of (-phobia) water (hydro-).
So, the kidnapper is worried that he might contract rabies from Buck's bite.
(Today, hydrophobia is most commonly used to mean "fear of going into or swimming in water," and rabies is used to mean the disease.)