Instrument for taking samples from internal organs

Claim 1

An instrument for taking tissue samples from internal organs of humans and animals comprising a tubular body having an open end and a closed end, a plunger mounted for axial movement within the body, said body and plunger constituting a vacuum pump, with said body also serving as a handle for the instrument, a cannula constituting a sampling portion of the instrument, said cannula having an outer diameter of about 0.4 mm, means detachably connecting the cannula to the open end of the body, a needle of homogeneous material, means resiliently supporting the needle in the plunger, said needle extending through the open end of the body into the cannula and terminating in a point located immediately outside the end of the cannula when the plunger is at the end of its stroke towards the open end of the body, the outer diameter of the needle and the inner diameter of the cannula being such as to provide a narrow annular gap between the needle and cannula, said gap allowing for a pressure balance between the cannula and the body upon movement of the plunger from the open end toward the closed end of the body yet preventing the passage of the tissue sample past the point of the needle during the movement of the needle with thee plunger, said body having an axial slot therein, means attached to the plunger and projecting through said axial slot, a member slidably mounted on the outside of said body to which said attaching means is secured, the length of the axial slot limiting the stroke of the plunger, and said body having an aperture in proximity to the open end of the body to provide communication between the body and the outer air, said aperture being closed when the plunger is adjacent the open end of the body but being exposed when the plunger moves toward the end of its stroke in the direction of the closed end of the body after a tissue sample has been drawn into the cannula to effect the pressure balance.