Initial practices involving experimentation with animals can be found in ancient Greece, but animal experimentation as understood in the modern world first emerged in the Renaissance. In the 19 th century, the French scientist Claude Bernard analysed the basis for animal experimentation using the Cartesian philosophical concept of animals being equivalent to machines. Yet as Claude Bernard's work on biology developed, it showed that animals, in particular the so-called sentient animals, did have forms of sensitivity and consciousness similar to humans. This led to the present-day moral concern with animal experimentation. The moral argument is expressed in philosophical terms in the Universal Declaration of Animal Rights and the law known as the "Three Rs", while the practical measures for implementation are set out in the European Directive 2010/63/EU on the protection of animals used for scientific purposes, and then as transposed and enforced in the different European Union Member States. This has led to improvements in the treatment of animals used for experimentation, and also allows scope for further improvements to be added in the future, particularly with alternative methods.