since Duke and Cornell are comparable academically...
http://www.aas.duke.edu/trinity/prehealth/faq/rcourses.html
24. Can I take Physics at my state school this summer instead of taking it here at Duke?
Probably. Compare it with Duke's physics courses. If you have questions, check with the Director of Undergraduate Studies in Physics. If you want to transfer it in, the forms and approval have to be completed in advance. See what's written earlier in this booklet on this subject. Remeber that you will be tested on physics for the MCAT etc. Therfore, you should make sure the course is a rigorous one.
25. Will med schools think poorly of me if I take a required class at another institution?
The answer to this will depend to some extent upon your record at Duke and your reasons for doing so. If you have chosen to take the bare minimum of science courses required to make application to medical school and then have taken some of those at a less demanding institution, the medical schools might question either your self-confidence, your abilities, or both. However, if you take most of your required courses as a part of a challenging curriculum at Duke, but choose to take a required course at another solid institution for financial, scheduling, etc. reasons, they are not likely to be too concerned. If the course is one that is tested on the MCAT, they may look to your MCAT score to be sure you were well prepared.