When did animal experimentation start?

The famous Greek doctor Galen (AD129-200) studied animals. William Harvey used animals 400 years ago to discover how blood circulated in the body. The 'modern' era of animal research started about 150 years ago with the rise of physiology as a science. But it was very different then - there were no anaesthetics or effective pain killers, so the animals suffered a great deal, as did patients. Imagine having your leg amputated (which was not uncommon - infections could be very serious before antibiotics) without anaesthetic.