Because dogs have a very large blood vessel running close the surface of their noses, when they breathe quickly, or pant, it brings air flowing in over that blood vessel again and again.
(dogs; have; a very large blood vessel running close the surface of their noses) (a very large blood vessel; running; close the surface of their noses) (they; breathe quickly; ) (it; brings; air flowing in over that blood vessel again and again; T:when they breathe quickly, or pant) (air; flowing; in; T:again and again)
dogs a very large blood vessel they it air
have running breathe quickly brings flowing
a very large blood vessel running close the surface of their noses
close the surface of their noses
air flowing in over that blood vessel again and again T:when they breathe quickly, or pant
in T:again and again