Panthino is Antonio's sensible servant. Like Lucetta, Panthino acts as a sounding board and dispenser of advice to his master, Antonio. In Act 1, Scene 3, Panthino advises Antonio to send Proteus abroad with all the other noblemen's sons:
'Twere good, I think, your lordship sent him thither.
There shall he practise tilts and tournaments,
Hear sweet discourse, converse with noblemen,
And be in eye of every exercise
Worthy his youth and nobleness of birth. (1.3.30-34)
Here, Panthino gives voice to the idea that young noblemen should travel abroad and hang out with other men of noble "birth" as a way to round out one's education. The question is, does Proteus actually learn anything in Milan?
After his conversation with Antonio, Panthino has a very small role in the play – namely, making sure Proteus and Lance catch their "ship" to Milan.