Yet across the gulf of space, minds that are to our minds as ours are to those of the beasts that perish, intellects vast and cool and unsympathetic, regarded this earth with envious eyes, and slowly and surely drew their plans against us.
Source: https://en.wikipedia.org/wiki/The_War_of_the_Worlds
I comprehend every part of that sentence except for the "beasts that perish" part.
What "beasts" (animals) do not "perish" (die)? Am I missing some sort of saying or reference here?