Direct Observation of the Mitral Valve Leaflets. Application of Pulse - Duplicator to Postmortem Calf's Heart The observation of the mitral valve during opening and closing is possible only by indirect laboratory methods. It is very difficult to keep the animal alive after the mitral valve operation in experimental surgical laboratuaries, and generally, these methods are quite expensive. On the other hand, it is not possible to try a numerous of surgical procedure on the same animal too. Application of pulse - duplicator to the postmortem calf's heart has been presented. Researcher can directly observe, and can take the photographs of the mitral leaflets' during the movements before and after applying the experimental procedure in this method. Some other advantages of this method has also been discussed.