" Most vertebrates and all of our fellow mammals have similar chemical and neurological mechanisms that transmit and control pain. Under stress or trauma, they display physiological reactions identical to ours - increased heartbeat and perspiration, higher cortisone levels in the blood, a release of endorphins, serotonin, and other natural opiates. Their bodies respond to anesthesia just as our bodies do, and of course they display vocalizations, defensive behavior, and bodily contortions similar to ours. We may add to this physical evidence the fact that veterinarians today routinely prescribe exactly the same antidepressant drugs to dogs, cats, pigs, horses and other animals, including Prozac, Ritalin, Xanax, and beta-blockers, and these drugs have exactly the same soothing effects on them as on us. "

― Matthew Scully , Dominion: The Power of Man, the Suffering of Animals, and the Call to Mercy