Context: the speaker is discussing the ways of illnesses.
atqui
emovit veterem mire novus, ut solet, in cor
traiecto lateris miseri capitisve dolore,
ut lethargicus hic cum fit pugil et medicum urget.
Translation: And yet,
the new [ailment] dislodges the old marvelously, as commonly occurs,
when a pain of the side or head of a sick person, is transferred to the heart,
as when here a drowsy patient becomes a boxer and attacks the doctor.
I’m unhappy with my understanding of the last line, in that I can’t account for ut … hic cum. My “as when here” is only guesswork.
I’m also unsure about the genitive construction lateris miseri capitisve. It is regular for dolor to take a genitive complement to indicate where the distress is located?
I think you have the sense of the last line pretty well: ut … cum “as when,” yes. The hic adds vividness (Gk. enargeia), a hallmark of Horace’s Satires. The dramatic form itself serves the same purpose. I read it as nominative here, but could well be wrong. Either way it invites the listener to envision the scene as taking place before his eyes. The movement of the line itself, starting lethargic and then becoming very dynamic, calls for a mimetic delivery.
If you can say caput dolet, “my head hurts,” you can speak of a dolor capitis. It’s called a subjective genitive, since caput would be the subject if dolor were a verb and not a noun. (As it is, it’s a “verbal noun.”)
Incidentally, emovit is not present but perfect, as meter and form conspire to tell us (long o, -it not –et). He’s explaining what happened to him.