Devices for sampling blood

A blood sampling device comprising:

• a cylindrical sampling tubule having front and rear ends;
• a piston displacable in air tight manner in said sampling tubule;
• a closure cap having a circumference, said closure cap being removably fitted to said front end of said cylindrical sampling tubule;
• an axially projecting tubular extension provided on said cap;
• a passage in said closure cap in communication with said extension;
• a piercable, self-sealing closure plug inserted in said extension;
• a guide sleeve having a diameter with an open end and a closed end, said guide sleeve being axially movable on said extension, a space separating a portion of said guide sleeve from said closure cap;
• a cannula having sharpened front and rear ends mounted in the closed end of said guide sleeve and axially aligned with said guide sleeve, said sharpened front end projecting forwardly from said guide sleeve for introduction into a patient and said sharpened rear end projecting rearwardly into said guide sleeve so that it can puncture said closure plug during relative axial movement between said guide sleeve and said extension;
• and
• means for venting the space between said guide sleeve and said extension.