From the book refereced by Les (above):
An animal is any living creature which can feel pain and
pleasure. All animals except men are called dumb animals be-
cause man alone has the power of articulate speech. Dumb ani-
mals can utter .sounds and cries of many kinds but not articu-
late or joined-together sounds. Beasts are the same as dumb
animals. Brutes is also only another name for dumb animals.
Dumb animals are also called the lower animals because they
are generally lower than man in intelligence and were once sup-
posed to be lower than man in all ways.
The entire text of the book can be found
HERE.