It was a perfectly logical (and legal) turn of events. While human alchemy was forbidden (not that Ed and Al didn't plan on breaking that taboo the minute they'd mastered the science), there were certain things that were permissible by law. Fusing humans into chimeras was theoretical but forbidden, and of course resurrection was right out. But medical alchemy? Healing broken bones? Nothing in the books said anything against that.
It should have been easy. Bone healed on its own after being set, after all. Why not speed up the natural process? And there was enough material for equivalent exchange—it was a clean fracture, after all, and Al had no problem setting the bone once Ed got the idea in his head. The bone just needed to fuse back together. It shouldn't have been a problem.
But still, Al had to ask, "Brother, are you sure this is a good idea?"
And Ed, grimacing from the pain of his broken leg, replied, "Of course, Al. There's nothing we have to give up here. It's all there to begin with."
"But Pinako says…"
"Pinako makes automail. If that's not surpassing medicine and playing God or whatever, I don't know what is. Now just do the transmutation!"
Reluctantly, Al activated the circle. There was a flash of light, Ed screaming, and then Teacher bursting out yelling.
"Just what the hell do you two think you're doing?" she roared.
It was too late. The transmutation finished and Ed's leg was healed. Feeling no pain, he was about to get to his feet when Izumi glared him into submission.
"We're sorry, Teacher," Al said. "We were training and Brother broke his leg. I set it, but we thought we could try to…"
"Al," Ed warned, preventing his younger brother from trying to take the blame. Izumi wouldn't believe him anyway; she knew that despite the fact that both Elrics were accomplished troublemakers, a plan this ridiculous could only come from Ed. Al would just get in trouble for lying. "I thought I could shorten the healing time with alchemy. The transmutation went just fine." And to prove his point, he stood up…and fell over, crumpled in pain.
"Your theory was sound according to the Law of Equivalent Exchange," Izumi declared. "But if you knew any anatomy or medicine, you'd know that the cells in your bones need calcium to rebuild. When your alchemy tried to increase the process, there wasn't enough calcium. Your bone is too soft now."
"Teacher, how can we fix this?" Al asked.
Izumi gave him a stern look and ordered, "Go into town and buy three quarts of milk. Sig will give you the money. Be sure that he or Mason comes here to carry your brother into the house."
"Three quarts of milk?" Ed repeated in horror.
"Yes," Izumi growled. "And you'll drink every last one. Three glasses each day at least, until your bones are hard again."
"I won't drink that stuff!" Ed shouted out of habit. But the look of fury on his teacher's face finally cowed him to the point that he muttered, "Yes, ma'am."
"When Al gets back, you are to start your three glasses," she insisted. "No complaints."
Three quarts and about one week later, and Ed was sitting out on the porch, sulking after a thorough beating in practice. Even though he'd just healed, Izumi refused to let his skills grow soft, and Al was as good as ever. The stars above him weren't as clear as they were back home in Risembool, but he could still see the Milky Way. He pouted as he thought of the fairytale his mother used to tell him and Al about the jealous goddess who spilled milk across the sky rather than feed the baby who wasn't hers. At least that kid didn't have to drink that disgusting liquid.
"Brother, are you okay?" Al checked, coming outside. "I didn't hit you too bad, did I?"
"Nah," Ed answered. "It takes a lot more than that to take me down."
Al grinned. "Didn't look like that when you went flying over my shoulder."
"That's just 'cause I've been hurt. I haven't practiced!"
Ed stood up and ruffled his younger brother's hair. "Come on, Al. We better go inside before Teacher starts yelling." But Al was staring at him in surprise. "What is it?"
"Brother, did you grow a few inches?" he asked. "I'm at your chin now."
Ed blinked for a moment before grinning. "See, Al? I told you I'd hit that growth spurt before long!"
"Maybe it's because of all that milk. It was fixing your broken leg, so maybe it fixed the rest of your bones too."
Ed's face fell. "Shut up, Al." Al grinned.
I do not own Full Metal Alchemist. This silly little piece resulted from a conversation with other members of the Diaries Guild, in which I brought up the question of how far human alchemy can go before it's illegal. Thanks to Shaun Garin and Lord Archive for suggestions.