The first regulations (1883) have been renewed twice (1933, 1972) and will soon be renewed once again (1986). They have always been influenced by two motivations: men's feeling of responsibility for animals on one hand and antiscientism or public suspicion against scientists on the other hand. The general rules concerning animal welfare (anaesthesia, reduction of number and harm, species selection etc.) have been constant for 100 years, but governmental control increases by the establishment of special licences (for each project, for the responsible scientist, for the location) by regular controls of the laboratories, by installing a permanent animal welfare officer in the institutions, by protocols, special taxes and increasing penalties. Out of different public ethical concepts about the use of animals, the law for the present agrees with those permitting to use animals for "reasonable purposes". But now the public opinion wants to change to "only for necessary" purposes; this especially concerns animal experiments causing severe pain. Philosophers and public have difficulties to find consentaneous reasons for the "necessity" of basic research. Each basic research in biology must be accepted as necessary because life is multifactorially organized and can be analyzed sufficiently only by random-like strategies to test not monocausally evidenthypotheses alone, but all reasonable possibilities.