The injection that entered Rei's body was a sign of the end of Arthur's brain that was drowning in a panic situation and his main focus to make the Alchemist potion.
After the injection the sharp needle was removed from Rei's skin who was unconscious on the Alchemist table, Arthur breathed a sigh of relief when he saw Rei's body regenerating quickly.
The three body part samples used by Arthur would look like illegal surgery performed by an unlicensed doctor. The work of Alchemists and doctors has two equal chasms, common morals and humanity.
Arthur's actions by taking three body parts that store memory genetic in a person's body look like torture and murder. The Alchemist potion created by Arthur may be an extraordinary potion that can bring miracles, but it is paid for with three body parts that feel pain when taken as raw materials for the Alchemist.
