While Breen and the other men are digging and talking about mosquitoes, his hair changes from being combed and uncombed between shots.
Dr. Carroll illustrates Major Gorgas' mindset as "he's on his way through the Panama Canal in a rowboat." This film is taking place in 1898, sixteen years before the canal was opened and six years before the U.S. (and the real Gorgas) even began work in the Canal Zone.