Needleless syringe

A needleless syringe for use in the needleless injection of particles into the skin of a vertebrate subject, the syringe comprising:

• a gas flow path arranged to receive gas from a gas source;
• a first convergence in said gas flow path for reducing the pressure of the gas flowing through said gas flow path;
• a particle inlet for introducing particles into said gas flow separately from the gas, said particle inlet being in communication with said gas flow path downstream of at least the start of said first convergence so as to allow a payload of particles to be drawn into the gas flow path via the particle inlet under the action of reduced pressure gas to become entrained in the gas;
• a gas/particle exit nozzle bounding said gas flow path for the acceleration of the drawn in particles entrained in the gas;
• and
• a powder chamber, containing at least one payload of particles, in communication with the particle inlet so as to enable the particles of a payload to be drawn into the gas flow path from said powder chamber along the passage of said particle inlet,
• wherein said powder chamber is configured to be moved so as to bring said particle payload into and out of communication with said particle inlet.