Hullin 51: Falling from a Roof, Falling from the Air

If/when an animal falls from a roof -- if it breaks its limbs, the question shifts to focus on whether the injury is common (like rheumatism) or unusual, like a broken spine. And the concern here is only for the common case. Also, a bird that fundamentally crashes on water is considered fine if it can swim the length of its body -- upstream. Plus, what if a bird falls into all kinds of other substances?