No joking... I was going to say that it sounds like you have your ethical/moral dilemma essay for Pitt if you should decide to apply there.
Cheating of this kind can derail a med school career. It has to be reported on the AMCAS and, in my experience, it is an automatic "red card" - you are out of the game.
Now, your question is, I think, should you tell?
Are you obligated to tell? (Does your school have an honor code that requires you to tell because to do otherwise would be to tolerate those who cheat?)
If you are not obligated by an honor code, do you have a duty or loyalty to your professor, to inform him of irregularities in the testing environment?
Do you have a loyalty to your fellow students, to protect them from institutional action that could harm their professional aspirations?
I think that you could go to the professor and suggest that the next time that he gives this exam he could distribute the periodic table along with the exam so that students do not have an opportunity to use crib notes written on the inside cover of the chemistry text. Tell him that you understand that it is a very common practice in his class and one that hurts students who are honest (because of the curve). Its a final exam so there may not be much he can do although he could hold the grades for all of the students and ask students to report, with their text books, for examination of the book before the grade is released.
This is the sort of thing that makes me hate teaching.
Good luck!