specific embodiments of the present invention and their advantages are best understood by reference to fig1 through 4 , where like numbers are used to indicate like and corresponding features . throughout the present application , the terms “ upstream ” and “ downstream ” are defined respectively with respect to the direction of flow of the extracted fluid from the removal component 1 to the collecting bag 3 . in the particular embodiments depicted in the figures , a device for extracting a biological fluid comprises removal component 1 for removing the fluid , a bag 2 containing an additive anticoagulant and / or preservation solution for the extracted fluid and a collecting bag 3 intended to receive the extracted fluid to which the anticoagulant and / or preservation solution is added . such a device is in particular intended to collect the whole blood taken from a donor by way of removal component 1 , for example formed by a needle . the anticoagulant and / or preservation solution is for example of the cpd type and is introduced into the bag 2 prior to extraction of the biological fluid . the collecting bag 3 and the bag 2 containing the solution have for example a similar structure including an external envelope formed by two sheets of plastics material connected together , for example by welding , at their periphery so as to define an internal volume intended to receive the content . the sheets are formed from weldable and sterilisable flexible biocompatible plastics material , for example polyvinyl chloride . the external envelope of each of the bags 2 , 3 is provided with at least one orifice 4 , 5 , 6 arranged so as to allow the supply of the internal volume and / or the distribution of the content of the bag 2 , 3 . the removal component 1 is associated at one end 7 of a first flexible tube 8 , the other end 9 of which is in fluid communication with the collecting bag 3 . this design enables the collecting bag 3 to be supplied in closed circuit with extracted fluid . the bag 2 containing the additive anticoagulant and / or preservation solution is associated , by way of an outlet orifice 4 , with one end 10 of a second flexible tube 11 , the other end 12 of which is in fluid communication with the collecting bag 3 . this design enables the collecting bag 3 to be supplied in closed circuit with anticoagulant and / or preservation solution . the tubes 8 , 11 are for example formed from dividable and weldable sterilisable biocompatible flexible plastics material , for example polyvinyl chloride . an extraction device according to the invention also includes a peristaltic pump 13 able to partially constrict respectively the first 8 and the second 11 tube in a constriction area 14 . the peristaltic pump 13 used is of a conventional type , namely including a motor 15 actuating a shaft 16 on which there are mounted one or more cylindrical rotors 17 , 18 and carrying rollers 19 . in this type of pump 13 , each rotor 17 , 18 is able to constrict a flexible tube disposed on the running path of the rollers 19 . the succession of compression and relaxation thus produced on the flexible tube causes the fluid to circulate inside the tube . the structure of this type of pump is well known to persons skilled in the art and will not be described any further in this description . according to one embodiment of the invention , the rate of constriction of the first 8 and second 11 tubes is substantially identical . in a specific embodiment , this characteristic is implemented using a single rotor 17 for constricting the two tubes 8 , 11 . in another specific embodiment , the two rotors 17 , 18 are designed to constrict respectively the two tubes 8 , 11 at an identical tangential speed when the shaft 16 rotates . in a variant , these two rotors 17 , 18 are identical . these two specific embodiments are described in more detail below . according to an exemplary embodiment of the invention , the ratio between the cross - section of the second tube 11 through which the additive solution passes and that of the first tube 8 through which the extracted fluid passes is substantially equal to the proportion in volume of additive anticoagulant and / or preservation solution to be added to the extracted biological fluid . when the pump 13 is actuated , the rollers 19 constrict each tube 8 , 11 with a substantially identical tangential speed so that the flow rate within each tube 8 , 11 is proportional to the cross - section through which the fluid passes . this is because the flow rate inside a tube is the product of the speed of flow of the fluid , that is to say here the tangential speed of constriction of the tube , and the cross - section of the tube through which the fluid passes . according to an embodiment of the invention , the collecting bag 3 is supplied with the extracted biological fluid and with the additive anticoagulant and / or preservation solution in the desired volume proportions . first , second and third specific embodiments of an extraction device are described below , in which the first 8 and second 11 tubes are arranged so as to allow the mixing of the anticoagulant and / or preservation solution with the extracted fluid downstream of the constriction area . thus the anticoagulant and / or preservation solution is never directed towards the patient , which prevents any accidental injection of this solution into the patient or donor . in the first specific embodiment of the extraction device , depicted in fig1 and 2 , the peristaltic pump 13 includes two identical cylindrical rotors 17 , 18 . the rotors 17 , 18 each carry rollers 19 able to constrict respectively the first 8 and the second 11 tubes . in a first variant of this first specific embodiment depicted in fig1 the first 8 and second 11 tubes are associated with the collecting bag 3 respectively by way of inlet orifices 5 , 6 . in a second variant of this first specific embodiment depicted in fig2 a junction 20 , for example a y junction , is provided downstream of the constriction area 7 so as to connect the first 8 and second 11 tubes to a first end 21 of a tube 22 . the second end 23 of the tube 22 is connected to an input port 5 of the collecting bag 3 . the cross - section of the tube 22 must be sufficient to prevent any overpressure in the device , but is not fixed at a precise value . in this variant the collecting bag 3 is supplied with extracted biological fluid and with anticoagulant and / or preservation solution by way of the tube 22 . in a second specific embodiment of the extraction device , depicted in fig3 the first 8 and second 11 tubes are associated in a sealed fashion in a tube 24 , the downstream end 25 of which is connected to an input port 5 of the collecting bag 3 . in the depicted embodiment the tubes 8 , 11 , 24 form a parallel double aperture assembly . this association is effected upstream of the constriction area 14 of the peristaltic pump 13 , which comprises a single cylindrical rotor 17 carrying rollers 19 able to constrict the tubes 8 , 11 , 24 . in a variant of the second specific embodiment , the first 8 and second 11 tubes are closed downstream of the constriction area 14 . the extracted fluid and the anticoagulant and / or preservation solution are then transported by the tube 24 from the downstream end 9 , 12 of the first 8 and second 11 tubes to the collecting bag 3 . in a third specific embodiment of the extraction device , depicted in fig4 the second tube 11 is introduced in a sealed fashion inside the first tube 8 so as to form an assembly of the concentric double aperture type . the downstream end 9 of the first tube 8 is then connected to an input port 5 of the collecting bag 3 . in this embodiment , the cross - section of the first tube 8 through which the extracted fluid passes is equal to the cross - section of the first tube 8 minus that of the second tube 11 . the introduction of the second tube inside the first tube is effected upstream of the constriction area 14 formed by the peristaltic pump 13 , which comprises a single cylindrical rotor 17 carrying rollers 19 able to constrict the first 8 and second 11 tubes . in a variant of the third specific embodiment , the second tube 11 is closed downstream of the constriction area 14 . the extracted fluid and the anticoagulant and / or preservation solution are then transported by the first tube 8 from the downstream end 12 of the second tube 11 to the collecting bag 3 . according to various embodiments of the invention , the collecting bag 3 can be incorporated , by way of an outlet orifice , in a more complex system , which includes for example other bags , tubes , clamps or filters . such a solution can make it possible , after the collection of the whole blood and possibly dissociation of the removal component 1 and of the bag 2 by cutting and welding the corresponding tubes 8 , 11 , 22 , 24 , to effect in closed circuit the filtration and separation of the whole blood into its various constituents . in a particular example , the device is intended to effect in closed circuit the extraction of the whole blood of a donor and the addition of an anticoagulant solution of the cpd type . according to the standard in force in france , after addition , the volume proportion of additive cpd solution of to whole blood should be 14 %. according to an embodiment of the invention in compliance with this standard , the ratio between the cross - section of the second tube 11 through which the solution passes and that of the first tube 8 through which the fluid passes is then fixed at 0 . 14 . for example , the cross - section of the first tube 8 may be 0 . 7 cm 2 while that of the second tube 11 is 0 . 1 cm 2 . in an additional embodiment of the invention , the peristaltic pump 13 is able to constrict the first 8 and second 11 tubes simultaneously . such an embodiment makes it possible to supply the collecting bag 3 with the extracted fluid and with the anticoagulant and / or preservation solution simultaneously so as to improve the mixing by stirring in the collecting bag 3 . the invention therefore makes it possible to effect the closed - circuit extraction of a biological fluid and the addition of an anticoagulant and / or preservation solution in a collecting bag 3 whilst having , at any time , a volume proportion of added solution in the extracted fluid which is fixed at the desired value . thus , whatever the quantity of biological fluid collected , the content of the collecting bag 3 is at a desired proportion so that it can be used for medical and other purposes . although only exemplary embodiments of the invention are specifically described above , it will be appreciated that modifications and variations of the invention are possible without departing from the spirit and intended scope of the invention .
an extraction device for a biological fluid with an additive solution in which it is desirable for the additive solution to be present in a particular volume proportion to the biological fluid . the volume proportion of the additive solution is determined by the ratio of cross sections of two tubes , one which supplies the biological fluid to a collecting bag and a second which supplies the additive solution to a collecting bag . the tubes are periodically constricted in constriction areas by a pump . the tubes are configured so that the additive solution and the biological fluid only mix downstream of the constriction areas , thereby reducing the risk of supplying the additive solution to the source of the biological fluid . in an exemplary embodiment the biological fluid is blood collected from a patient or donor and the additive solution is an anticoagulant and / or preservation solution .