by Jessica Martini, Christie DeBernardis & Christina Bossinakis The elite Book 1 section of the Keeneland September Sale, which began with a powerhouse session Monday, maintained its energy all the way through to the end of Tuesday's second session. After nine yearlings sold for $1 million or more Monday, a further 13 horses topped that mark during Tuesday's session, led by a $1.8-million son of Constitution. "Coming out of day one, I think that momentum was almost euphoric," said Keeneland Vice President of Sales Tony Lacy. "Coming into day two,...