the preferred embodiments of the present invention are described hereinafter with reference to the drawings . the lancing device 1 of the present embodiment forms body fluid extraction holes ( micropores ) in the skin of a subject by installing a sterilized fine needle tip 6 so that the needles of the fine needle tip 6 abut the skin of the subject . the body fluid ( interstitial fluid ) exuded from the micropores formed in the skin of the subject by the lancing device 1 and the fine needle tip 6 is collected in an extraction medium , the glucose concentration in the interstitial fluid is calculated by measuring the extraction medium by a glucose analyzer ( not shown in the drawing ) and estimating the auc based on this calculated value so that a diabetic patient can , herself , monitor the estimated auc to manage her condition . the lancing device 1 forms a plurality of minute extraction pores through the stratum corneum of the epidermal layer of the skin but does not reach the vascular plexus in the dermis to extract interstitial fluid from the micropores . fig1 and 2 are perspective views showing the exterior structure of the lancing device of the present embodiment . the lancing device 1 is configured by a main body section 2 and a cover section 3 which covers the main body section 2 , and is substantially cylindrical overall . the cover section 3 is capable of sliding in the longitudinal direction relative to the main body section 2 . that is , the main body section 2 and the cover section 3 are relatively slidable in the longitudinal direction so that the main body section 2 can be pulled from the cover section 3 and the main body section 2 can be housed within the cover section 3 . fig1 shows the main body section 2 entirely housed within the cover section 3 , whereas fig2 shows the main body section 2 pulled from the cover section 3 . the main body section 2 has a cylindrical base 21 . a cylindrical step portion 22 extends from the base 21 and has a diameter that is coaxial and slightly smaller than the diameter of the base 21 , and a cylindrical ejecting portion 23 ultimately extends from the step portion 22 and has a diameter that is coaxial and slightly smaller than the diameter of the step portion 22 . an ejection aperture 23 a is provided in the ejecting portion 23 , to allow the fine needle tip which forms micropores in the skin of the subject to be launched from the ejection aperture 23 a . a cylindrical inner housing portion 24 , which has a diameter that is coaxial and smaller than the diameter of the base 21 , extends from the base 21 from the side opposite the step portion 22 . a mechanism for ejecting the fine needle tip is accommodated within the inner housing portion 24 . the cover section 3 is cylindrical with the same diameter as the base 21 , and is mounted on the main body section 2 so as to cover the inner housing portion 24 . the cover section 3 has an inner diameter that is slightly larger than the outer diameter of the inner housing portion 24 , and is slidable in the longitudinal direction relative to the inner housing portion 24 . in other words , the main body section 2 is slidable in the longitudinal direction relative to the cover section 3 . when the inner housing portion 24 is entirely covered by the cover section 3 ( the condition shown in fig1 is hereinafter referred to as “ closed condition ”), the end of the cover section 3 abuts the base portion 21 ( at this time , the position of the main body section 2 relative to the cover section 3 is hereinafter referred to as “ first position ”). a part of the inner housing portion 24 is exposed when the cover section 3 is moved relative to the main body section 2 in a direction that separates the base 21 and the cover section 3 from the closed condition . this condition ( hereinafter referred to as “ open condition ”) is shown in fig2 . the cover section 3 is a part which the user holds when using the lancing device 1 . the cover section 3 is cylindrical in shape as described above to be easy to hold by the user . the cover section 3 has an overall length of 100 mm and an external diameter of 30 mm so as to be easy to hold for the average adult . note that the size and shape of the cover section 3 is not specifically limited to these dimensions , and preferably will be cylindrical with a length of 90 mm or more and less than 110 mm for ease of grasping in a hand of the user . when the cover section 3 is cylindrical , the major diameter is preferably 10 mm or more and less than 50 mm . fig3 is a perspective view of the external structure of the main body section 2 with the cover section 3 removed . an operating section 4 is provided at the end of the main body section 2 on the opposite side from the ejecting portion 23 . the operating section 4 may be , for example , a button . the main body section 2 is described below with the ejecting portion 23 side referred to as the downstream side and the operating section 4 side as the upstream side . as shown in fig3 , the inner housing portion 24 is provided with a long slide hole in the longitudinal direction , that is , the vertical direction , of the inner housing portion 24 . as shown in fig2 and 3 , a pressing member 51 is provided within the inner housing portion 24 . the pressing member 51 has a screw hole 51 a , and a screw 31 for connecting the cover section 3 and the pressing member 51 is screwed into the screw hole 51 a through a slide hole 25 . the pressing member 51 is provided with a protrusion 51 b which protrudes to the outside , and the protrusion 51 b is inserted in the slide hole 25 . that is , the screw 31 and the protrusion 51 b are movable along the slide hole 25 , thereby regulating the movement direction of the cover section 3 which is connected to the pressing member 51 in the vertical direction . fig4 is a frontal view of the exterior of the lancing device in the closed condition , and fig5 is a front sectional view showing the interior of the lancing device in the closed condition . the protrusion 51 b is provided below the bottom end of the cover section 3 . that is , the bottom end of the cover section 3 abuts the top end of the base 21 and the protrusion 51 b intrudes to the inner side of the base 21 when the cover section 3 is in the closed condition . the bottom end of the pressing member 51 is bent in an l - shape to form a contact portion 51 c . a mounting member 52 for mounting the fine needle tip 6 is arranged inside the inner housing portion 24 , and a compression spring 54 for exerting a force on the mounting member 52 is arranged above the mounting member 52 . the condition shown in fig5 is a condition in which the compression spring 54 exerts a force on the mounting member 52 ( referred to below as “ de - energized condition ”). that is , the position of the mounting member shown in fig5 is the bottom limit position , and the length is the natural length such that a load is not exerted by the compression spring 54 when the mounting member 52 is at the bottom limit position . the mounting member 52 has two protrusions 52 a and 52 b , as shown in fig5 . when the cover section 3 is lifted upward and the lancing device 1 transitions from the closed condition to the opened condition , the contact portion 51 c of the pressing member 51 comes into contact with the protrusion 52 a on the bottom side of the mounting member 52 . the mounting member 52 is pressed by the pressing member 51 and moves upward when the cover section 3 is lifted . when the mounting member 52 moves upward , the compression spring 54 is compressed by the bottom end of the compression spring 54 being pressed upward by the mounting member 52 . thus , the compression spring 54 exerts a downward force on the mounting member 52 . two opposed guide parts 55 are provided on the inner wall of the inner housing portion 24 . fig5 shows only one of the two guide parts 55 . a gap extending in the vertical direction is formed between the two guide parts 55 , and the mounting member 52 is arranged between the two guide parts 55 . the movement direction of the mounting member 52 is regulated in the vertical direction by the gap between the two guide parts 55 . a locking member 53 is provided above the mounting member 52 , as shown in fig5 . the locking member 53 is rotatable on an axis 53 d which extends in the front - to - back direction . a hook 53 a is provided on the locking member 53 , and the locking member 53 exerts a force via a spring ( not shown in the drawing ) so that the hook 53 a is positioned on the bottom side in the natural position . fig6 is a side sectional view on the a - a line of fig4 ; when the lancing device 1 is in the closed condition , the bottom end of the cover section 3 and the top end of the base 21 are in contact or very near contact , as shown in fig6 . in this condition , the protrusion 51 b of the pressing member 51 intrudes to the inner side of the base 21 as described above . a concavity 21 a is formed on the inner side of the base 21 , and the protrusion 51 b engages the concavity 21 a at this time . a convexity 21 b is provided at the top side of the concavity 21 a , such that the protrusion 51 b must override the convexity 21 b and move upward when the engagement is released from the condition of the protrusion 51 b engages in the concavity 21 a . that is , the protrusion 51 b must override the convexity 21 b for the lancing device 1 to transition from the closed condition to the opened condition . the force required to accomplish this override is 3 n in the present embodiment . note that the force required to release the engagement of the main body section 2 and the cover section 3 of the lancing device 1 is not limited to 3 n , but preferably is 2 n or greater but less than 5 n . fig7 is a frontal view of the exterior of the lancing device in the opened condition , and fig8 is a front sectional view showing the interior of the lancing device in the opened condition . fig9 is a side sectional view on the b - b line of fig7 . when the cover section 3 is lifted upward relative to the main body section 2 with a force of 3 n or greater , the protrusion 51 b which is engaged in the concavity 21 a overrides the convexity 21 b , and the engagement of the cover section 3 and the main body section 2 is released ( refer to fig9 ). when the cover section 3 is lifted upward , the bottom end of the cover section 3 separates from the top end of the base 21 and the inner housing portion 24 is exposed ( refer to fig7 ). at this time , the pressing member 51 also moves upward together with the cover section 3 relative to the main body section 2 , and the protrusion 51 b is exposed from the slide hole 25 of the inner housing portion 24 . the mounting member 52 is lifted upward when the cover section 3 is lifted upward while the contact portion 51 c of the pressing member 51 contacts the protrusion 52 a on the bottom side of the mounting member 52 , as mentioned above . an inclined portion 53 b is provided on the bottom side of the hook 53 a of the locking member 53 . when the mounting member 52 moves upward within the inner housing portion 24 , the mounting member 52 approaches the locking member 53 and the protrusion 52 b on the top side of the mounting member 52 comes into contact with the inclined portion 53 b of the locking member 53 . then , when the ascent of the mounting member 52 continues , the inclined portion 53 b is pressed by the protrusion 52 b and the locking member 53 is rotated on the pivot shaft 53 d against the exerted force . hence , when the protrusion 52 b overrides the inclined surface 53 b , the locking member 53 is rotated in the opposite direction by the exerted force and returned to the natural condition . the protrusion 52 b therefore engages the hook 53 a of the locking member 53 ( refer to fig8 ). as shown in fig7 , when the cover section 3 is lifted upward relative to the main body section 2 until the screw 31 connecting the cover section 3 and the pressing member 51 is positioned near the top end of the slide hole 25 ( at this time the position of the main body section 2 relative to the cover section 3 is referred to as “ second position ” below ), the protrusion 52 b of the mounting member 52 therefore engages the hook 53 a of the locking member 53 . at this time the mounting member 52 receives the force exerted by the compression spring 54 ( referred to as “ energized condition ” below ). when the mounting member 52 is in the energized condition , the main body section 2 is movable between the first position and the second position . fig1 is a front sectional view showing the interior of the lancing device 1 with the cover section 3 closed when the mounting member 52 is in the energized condition . when the main body section 2 is moved upward from the second position while the mounting member 52 is energized and the energized condition is locked by the locking member 53 , the contact portion 51 c of the pressing member 51 separates from the protrusion 52 a of the mounting member 52 and moves downward relative to the protrusion 52 a ( the protrusion 52 a moves upward relative to the contact portion 51 c ). that is , the cover section 3 is closed with the mounting member 52 in the energized condition . the main body section 2 moves upward accurately relative to the cover section 3 because the pressing member 51 and the movement of the cover section 3 are regulated in the vertical direction by the slide hole 25 at this time . the upward movement of the main body section 2 causes the protrusion 51 b of the pressing member 51 to override the convexity 21 b provided on the inner side of the base 21 , the protrusion 51 b then engages the concavity 21 a and the main body section 2 arrives at the first position . hence , the condition shown in fig8 transitions to the condition shown in fig1 . when the mounting member 52 is in the energized condition and the main body section 2 is at the first position , the lancing device 1 enters the operational condition in which the device can be operated by the user . when the operating section 4 is operated downward while the lancing device 1 is in the operational condition ( operating section 4 is pressed down ), the lock held by the locking member 53 is released , the mounting member 52 is actuated by the force exerted by the compression spring 54 , and the fine needle tip 6 is launched downward . fig1 is a front sectional view showing the interior of the lancing device in the operational condition . the operating section 4 is mounted on the inner housing portion 25 and moves in vertical directions . a support panel 56 which extends laterally is fixedly attached to the inner wall of the inner housing portion 25 at a position below the operating section 4 . a vertical panel portion 41 is provided at the bottom of the operating section 4 , and the panel portion 41 extends below the support panel 56 . a protrusion 42 is provided on the panel portion 41 . an inclined portion 53 c is provided on the surface of the locking member 53 which faces the panel portion 41 . the inclined portion 53 c of the locking member 53 comes into contact with the protrusion 42 of the panel portion 41 . the operating section 4 is usually protrudes from the main body section 2 because the locking portion 53 receives an upward force via a spring through the protrusion 42 and the inclined portion 53 c . when the operating section 4 is pressed downward , the panel portion 41 moves downward relative to the support panel 56 , the inclined portion 53 c is pressed down by the protrusion 42 , and the locking member 53 is rotated on the pivot shaft 53 d against the exerted force . the force required to operate the operating section 4 in the downward direction , that is , the force necessary to press down the operating section 4 against the force exerted by the locking portion 53 , is 6 n in the present embodiment . note that the force required to press down the operating section 4 is not limited to 6 n , and such force is preferably 5 n or greater but less than 10 n inasmuch as the force necessary is at least greater than the force required to release the engagement between the main body section 2 and the cover section 3 of the lancing device 1 ( a force of 3 n in the present embodiment ). when the operating section 4 is pressed down and the panel portion 41 moves downward , the panel portion 41 opposes the top part of the locking member 53 . then , when the descent of the operating section 4 continues , the inclined portion 53 c is pressed by the protrusion 42 and the locking member 53 is rotated on the pivot shaft 53 d against the exerted force . hence , the engagement is released between the protrusion 52 b of the mounting member 52 and the hook 53 a of the locking member 53 , the mounting member 52 with the fine needle top 6 mounted thereon is forced downward by the compression spring 54 , and the fine needle tip 6 is launched . the operation of the lancing device 1 is described below . the subject first mounts the fine needle tip 6 on the mounting member 52 from the ejection aperture 23 a . the subject then shifts the lancing device 1 from the de - energized condition to the energized condition . that is , the subject holds the cover section 4 of the lancing device 1 in the hand ( for example , the right hand ) and grasps the base 21 of the main body section 2 with the other hand ( for example , the left hand ), then moves the cover section 3 relative to the base 21 so as to pull the closed cover section 3 from the base 21 . the main body section 2 is thus moved from the first position to the second position . while the main body section 2 moves from the first position to the second position , the pressing member 51 moves upward inside the inner housing portion 24 , the contact portion 51 c comes into contact with the protrusion 52 a of the mounting member 52 , and the mounting member 52 is pressed upward by the pressing member 51 . the compression spring 54 is therefore compressed , and the mounting member 52 is ultimately pulled up against the force exerted by the compression spring 54 . the protrusion 52 b on the top side of the mounting member 52 comes into contact with the inclined portion 53 b of the locking member 53 , the inclined portion 53 b is pressed by the protrusion 52 b , and the locking member 53 is rotated on the pivot shaft 53 d . when the protrusion 52 b overrides the inclined portion 53 b , the locking member 53 returns to the natural condition and the protrusion 52 b engages the hook 53 a of the locking member 53 . hence , the mounting member 52 becomes energized . the subject then moves the main body section 2 from the second position to the first position relative to the cover section 3 so as to close the cover section 3 of the energized lancing device 1 . that is , the subject moves the cover section 3 with one hand to bring it near the base 21 which is held in the other hand so that there is contact or near contact between the bottom end of the cover section 3 and the top end of the base 21 . hence , the lancing device 1 becomes operational . when the lancing device 1 becomes operational , the subject holds the cover section 3 in one hand ( for example , the right hand ), and presses the bottom end of the lancing device 1 , that is , the end provided with the ejection aperture 23 a of the ejecting portion 23 , against the body ( for example , the left arm ) of the subject . thus , the main body 2 of the lancing device 1 is pressed upward , that is , the mounting member 52 ( fine needle tip 6 ) is pressed in the opposite direction to the direction in which the force is exerted by the compression spring 54 , and the downward movement of the main body section 2 is regulated . as described above , the operating section 4 is operated by the thumb of the hand in which the subject holds the cover section 3 when the main body section 2 is pushed upward . when a downward force is applied to the operating section 4 , this force is transmitted to the main body section 2 through the support panel 56 . that is , the downward force on the main body section 2 functions as a force in the direction of separation from the cover section 3 . however , since the main body section 2 is pressed against the body of the subject at this time , a reaction force to the downward force is generated , and the main body section 2 does not move relative to the cover section 3 so as to remain stationary at the first position . as described above , a force of 6 n is required to operate the operating section 4 . therefore , when a downward force of 6 n or greater is applied to the operating section 4 , the locking member 53 rotates on the pivot shaft 53 d . this action releases the lock of the locking member 53 , the mounting member 52 is actuated by the force exerted by the compression spring 54 , and the fine needle tip 6 is launched downward . a plurality of fine needles protrude from the bottom surface ( the surface facing the skin , referred to as “ micropore forming surface ” below ) of the fine needle tip 6 . the fine needles of the fine needle tip 6 have a length ( for example 0 . 3 mm ) sufficient to pass through the stratum corneum of the epidermal skin but not reach the vascular plexus in the dermis . the micropore forming surface of the fine needle tip 6 abuts ( impacts ) the skin of the subject and forms a plurality of micropores in the skin of the subject . the operation of the lancing device 1 is described below when a force is applied downward on the operating section 4 while the bottom end of the operational lancing device 1 is not pressed against the body of the subject , that is , the downward movement of the main body section 2 is not regulated . when a downward force is applied to the operating section 4 due to the subject trying to operate the operating section 4 or inadvertently touching the operating section 4 when the main body section 2 of the lancing device 1 is not being pressed upward , this force is transmitted to the main body section 2 through the support panel 56 . that is , the downward force on the main body section 2 functions as a force in the direction of separation from the cover section 3 . at this time a force of 3 n is required to release the engagement between the base 21 and the protrusion 51 b of the pressing member 51 ; since a force of 6 n is required to operate the operating section 4 , the operating section 4 does not operate when a downward force of 3 n or greater is applied to the operating section 4 , and the engagement between the base 21 and the protrusion 51 b is not released . therefore , the main body section 2 moves from the first position to the second position relative to the cover section 3 , and the lancing device 1 is opened . at this time the fine needle tip 6 is not launched because the operating section 4 does not operate . that is , according to the lancing device 1 of the present embodiment , when the bottom end of the lancing device 1 is not pressed against the body of the subject , the mechanism which launches fine needle tip 6 of the lancing device 1 will not operate even when a downward force is applied to the operating section 4 due to misuse or the like , and the main body section 2 and the cover section 3 are pulled apart . the user inadvertently launching the fine needle tip 6 is therefore prevented . note that although the embodiment described above is configured with the operating section 4 provided at the end on the opposite side from the ejection aperture 23 a of the lancing device 1 , the present invention is not limited to this configuration . the position of the operating section is discretionary insofar as it is operational in the same direction as the direction of separation of the main body section 2 from the cover section 3 . for example , the operating section may be provided on a side surface of the cover section 3 . although the drive source of the mounting member 52 and the fine needle tip 6 mounted thereon is a compression spring 54 in the above embodiment , the present invention is not limited to this configuration . an elastic body other than a compression spring , such as rubber , tension spring , air spring or the like also may be used as the drive source of the mounting member 52 and the fine needle tip 6 . furthermore , a power generator such as a pneumatic cylinder or more may be used , rather than an elastic body , as the drive source of the mounting member 52 and the fine needle tip 6 , wherein the power generator generates a drive force in response to the operation of the operating section 4 to drive the mounting member 52 and the fine needle tip 6 . although a force of 3 n is required to release the engagement between the cover section 3 and the main body section 2 , and a force of 6 n is required to operate the operating section 4 in the embodiment described above , the present invention is not limited to this configuration . however , it is preferable that the difference between the force required to operate the operating section 4 and the force required to release the engagement between the cover section 3 and the main body section 2 is 1 n or greater but less than 6 n . when a downward force is applied to the operating section 4 while the main body section 2 of the operational lancing device 1 is not being pressed upward , the mechanism which launches the fine needle tip 6 of the lancing device 1 is reliably prevented from operating and the main body section 2 and the cover section 3 can be pulled apart by because the difference between the force required to operate the operating section 4 and the force required to release the engagement between the cover section 3 and the main body section 2 is 1 n or greater . furthermore , handling complexity is caused by an extreme difference between the force required to operate the operating section 4 and the force required to release the engagement between the cover section 3 and the main body section 2 can be avoided because difference between the force required to operate the operating section 4 and the force required to release the engagement between the cover section 3 and the main body section 2 is less than 6 n . although the above embodiment has been described in terms of piercing the skin of a subject by a fine needle tip 6 , the present invention is not limited to this configuration . a configuration which lances by mounting a lancing unit with a conventional needle may also be applied . although the above embodiment is described in terms of operation by the subject herself , the present invention is not limited to this configuration . the lancing device also may be operated by a person other than the subject .