Devices for the expression of bodily fluids from an incision

A device (47) for extracting body fluid from a skin incision, said incision being in an incision and said device comprising: a body defining a cavity; and bistable element extraction pressure (49) connected to said interior cavity adjacent to the body and including a portion having a first and second position stable tion, it said part being in the first stable position outwardly cambered to said body, do that part stagnant in the second stable position inverted and received within the cavity of said body, said portion including an outer surface attached to the skin and defining an opening (55) communicating the outer surface attached to skin and the cavity of said body, so that the surface pasted to the lace her skin and within said drag as said portion passes from the first to the second position.