1 1/2 lemons, very thinly sliced crosswise and seeded
In a small bowl, combine 1/2 tablespoon of the lemon juice and 1 tablespoon of the olive oil. In a large bowl, toss the arugula with the parsley, basil, chives and mint.
Put the veal scallopine on 2 large baking sheets and season both sides with salt and pepper. Dust with the flour and shake off the excess.
In each of 2 large skillets, heat 2 tablespoons of olive oil until shimmering. Add the scallopine to the skillets in a single layer, without crowding, and cook over high heat until browned, about 2 minutes per side. Transfer to a platter and keep warm. Add the remaining 1 tablespoon of olive oil to 1 of the skillets and cook the remaining veal.
Pour off the oil and add the butter to the skillet. Cook over moderately high heat until the butter starts to brown, about 3 minutes. Add the lemon slices and the remaining 2 tablespoons of lemon juice to the skillet and cook until the slices sizzle, about 1 minute. Season the sauce with salt and pepper. Transfer the veal to plates and pour the sauce on top. Toss the herb salad with the vinaigrette, mound alongside the veal and serve right away.