randomengine
Banned
Enough people in the thread have given you reasonable explanations as to why it happened. The fact is, you're insistent on bringing up things like jackets and bacteria to disprove the theory. Yes, for all we know, if a cat was caught in a tear and lost its leg, the cat would be able to jump between timelines. But you're going into very nitpicky details.
The Luteces were one-of-a-kind scientists that designed the tear machine in the first place. Most of the explanations in the game (why Comstock aged faster, was sterile, why Elizabeth had powers) were Lutece's theories, not facts. The /fact/ is, Comstock killed the Luteces before they could research more with Elizabeth. The entire point of him killing Lady Comstock and the Luteces was Comstock wanted the tears and Elizabeth to himself and not for anybody else to gain her powers. He wanted to groom her to become the all-powerful God and only her, after he'd brainwashed her into believing him. He didn't care about understanding her, he only wanted to fulfill his prophecy of doom.
Hell, cut out the middle man and have Comstock cut his own pinkie off with a tear either by the Luteces or his own "daughter". He might even be able to find a way to prevent his own death.