Animals are surrogates for humans. The basic reason for animal trials is to determine two issues before any new compound is introduced into a human: safety and efficacy, whether a compound is safe for human ingestion and also whether or not a product works for its intended purpose. Really that process begins way before we get to animals. But at some point in the process it is critical to understand how a compound, let's say, a hypertension medication, works in a whole living system. You can't just determine how it works on blood pressure or the heart. You need to know how it would affect all the organs. That really is the whole purpose of using a complex biological system known as an animal.