NET
19 For the power of the horses resides in their mouths and in their tails, because their tails are like snakes, having heads that inflict injuries.
Darby
19 For the power of the horses is in their mouth and in their tails: for their tails [are] like serpents, having heads, and with them they injure.
KJV
19 For their power is in their mouth, and in their tails: for their tails [were] like unto serpents, and had heads, and with them they do hurt.