In the photo above, Max Factor, Hollywood make-up specialist (left) and Dr. J. R. Pratt, chemist, we

In the photo above, Max Factor, Hollywood make-up specialist (left) and Dr. J. R. Pratt, chemist, were testing a new lipstick on a shaven guinea pig (circle) in 1939. A baby guinea pig was used for the test because its under skin is ten times more sensitive than that of a human being.