who becomes jim's mentor at the university?

While Jim is in college, Latin teacher, Gaston Cleric
becomes Jim's mentor.  The two spend a great deal of time conversing and eventually, Jim
follows Gaston to Harvard to complete his education.  Gaston is a passionate teacher who
is able to breathe life into the classics for his students and for Jim.  At the end of
the novel, the reader learns that Gaston dies of pneumonia.