Hullin 32: Invalid Shechitah

2 mishnayot! 1 - A person is slaughtering an animal and the knife falls and he picks it up to complete the slaughtering... as long as the shechitah is completed in the time that it would take to slaughter the animal to begin with, that's kosher. If it takes more time, then it's not a valid shechitah. But different animals - and fowl - take different amounts of time to do the shechitah. Does the statement of "shechting the animal" apply to every animal/bird, or does the time fluctuate depending on the animal/bird at hand? 2 - What if only one of the simanim/pipes were severed correctly, of the esophagus and trachea? If the animal is unfit, it is presented as a treyfa - but then the Gemara addresses such cases as a neveilah.