aspirating is way different. your pulling air/blood/ nothing into the needle from your own body and putting it back in with nothing ever leaving the body. take a dirty needle that you stuck into you body it will have micro organisms and bacteria on it then stick it in a vial where might be some air and boom you got yourself a live culture going on, not smart. Equate it to pulling a sealed package of meet, take a pound out and let it sit for a day then put it back into the sealed package.