The invention relates to an instrument ( 1 ) for measuring the elasticity of a human or animal organ located behind the ribs ( 2 ). The inventive instrument is of the type that consists of a casing ( 3 ) comprising an actuator, the end of which is equipped with a transducer ( 4 ) that is actuated in order to measure the elasticity of the organ. The invention is characterised in that the measuring instrument ( 1 ) also comprises a means ( 7 ) for centring the transducer ( 4 ) between the ribs ( 2 ).
