Athenian Pull

When injecting drugs into a vein, after one draws blood into the syringe, instead of injecting all of the contents of the syringe at once, One injects half the contents and then pulls more blood into the syringe before injecting the rest or a little more since sometimes this can be repeated two to three times. It assists in the mixture of the drugs in the syringe with the blood from the vein and making sure the syringe needle remains in a vein.