transformation into a tension wave under acoustically 34 soft 34 condition these tension waves are then reflected in an acoustically 34 hard 34 manner from acoustically reflective body 3 in the same way as the compression waves and thus travel back as tension waves to the compacta spongiosa of bone 1 since this material is also acoustically hard in comparison to the tissue or fat in boundary surface gap 2 this means that the wave is also reflected back by this surface of the bone accordingly in the gap of volume the tension wave components are superimposed by multiple reflections depicted by the arrows in the lower portion of fig1 if the gap 2 is small enough such as less than 5 millimeters temporary standing waves form in the boundary surface gap by a superimposition and by the vibration of the two boundary surfaces these standing waves vibrate in various modes and amplitudes as shown in the lower portion of fig1 the temporary standing waves and the superimposition of the tension wave components act therapeutically by transforming undifferentiated cells by bringing blood into the gap with the resulting catabolic and anabolic processes by drawing bone splinters or microfractures into the gap which then serve as nucleation seed for the process of osteogenesis and exerting tensile and compressive mechanical stress on the boundary surfaces whereupon these surfaces also react with osteogenesis the machine 11 shown in fig6 contains a device 20 such as that shown in fig2 for generating a shock wave 4 one device suitable for generating such a shock wave is shown in u s pat no 2 559 227 in this reference a spark gap 9 and a semi ellipsoid.