The invention relates to an apparatus, a method and a knife for loosening a plucks set including heart and lungs from a carcass, especially a pig car¬ cass . An apparatus for pulling a plucks set loose from a carcass is described in DK-B-173879 (Slagteri- ernes Forskningsinstitut) . This apparatus is used on carcasses hung by the hind legs and where the abdomi¬ nal cavity has been cleared. Viscera and possibly also some organs have been removed and a full or re¬ duced plucks set is hanging out through the incision in the abdomen, chest and throat. A holding device is intended to be brought up around the windpipe and gullet from below to thereby arrange them in a slot in the holding device. The holding device with the plucks set is then pulled away from the carcass. The pull causes the windpipe and gullet to be stretched and at the same time loosened from the carcass. When the pull is sufficiently strong the windpipe and gul¬ let will be pulled free of the carcass all the way down to the larynx. The plucks set is finally cut free by cutting the windpipe and gullet while these are still stretched out. From a hygienic point of view the cutting of the gullet is, however, not expedient as it is a part of the digestive system, which contains a lot of bac- teria. It is therefore an object of the invention to provide an apparatus and a method for loosening a plucks set including heart and lungs without cutting the gullet. This object is obtained according to the inven¬ tion by an apparatus comprising cutting means de¬ signed for loosening the larynx from the inside of the carcass and a device for moving the cutting means in a substantially vertical direction. The vertical movement of the cutting means preferably corresponds to a direction substantially in parallel with the palate of the carcass, when it is hanging by the hind legs, as is the standard in most slaughterhouses. For most purposes it will be sufficient, if the direction of movement of the cut¬ ting means form an angle of 0° to.30° with the verti¬ cal. However, if the carcass is hung or oriented dif- ferently, when the apparatus is to be used, another direction of movement may be appropriate. In the fol¬ lowing, this applies whenever a direction is indi¬ cated as being vertical, and similar considerations also apply to all other specifications of direction given herein. To achieve the loosening the apparatus performs a cut behind the larynx. To achieve a removal of the plucks set further cuts can be made along the two sides and in front of the tongue enabling a freeing of the plucks set with tongue, windpipe and gullet from the carcass. The latter two types of cuts may be performed manually by means of a knife or by means of tools mounted in the apparatus. Movement of cutting means may be achieved using cylinder units, motors or the like. When the larynx and the tongue are cut loose from the carcass without cutting the windpipe and gullet, they can be removed together with the plucks set . Subsequent separate removal of the tongue and larynx is thus rendered superfluous. As the intended position of the cut behind the larynx, along the backside of throat, may vary due to size and race variation between different slaughter animals it is preferred that the apparatus comprises a positioning device for controlling positioning of the cutting means. The positioning device can be de¬ signed in several ways but a particularly precise po- sitioning is achieved when the positioning device comprises two pointed projections having a mutual distance corresponding substantially to the distance between choanaes of the carcass, the choanaes being the openings of the nasal cavity towards the wind- pipe. When the carcass is hung by the hind legs, the choanaes are located immediately behind the larynx and since their location in relation to other parts of the head is well-defined, a very precise cutting may be achieved by positioning the cutting means in relation thereto. The cutting means may include a knife with a cutting edge along the lower edge of the knife blade. Again, the cutting edge being located on the edge of the knife presuppose that the carcass is hung from the hind legs, meaning that a different arrangement of the cutting edge may be appropriate if the carcass is oriented differently. If such a knife is used to¬ gether with a positioning device as described above it will be possible to advance the knife from a posi- tion above the larynx close to the spine to a posi¬ tion where it is located close to the palate . The knife may be of many different designs but when the knife is advanced in parallel with the pal- ate it is expedient that at least a part of the knife blade curves around an axis, which is substantially parallel to the direction of movement of the knife during cutting. Hereby the risk of the knife damaging the palate or the surrounding tissue as well as the risk of it hitting parts of the cranium is reduced. With a view to further adaptation to the anatomy of the carcass the design of the knife blade may be fur¬ ther modified. It may for example comprise more than one curved parts, which may have different radix of curvature and curve around different axes, these axes being parallel to the intended direction of movement of the knife. In addition, the cutting edge may curve around an axis, which is perpendicular to the in- tended direction of movement of the knife. During cutting by means of the apparatus ac¬ cording to the invention it is preferred that a pull is exerted on the windpipe and gullet e.g. by a hold¬ ing device exerting a pull on the windpipe and gullet away from the carcass and which has two holding mem¬ bers and means for moving the holding members . The device may be of the design described in the DK pat¬ ent mentioned above, comprising a set of plates with a slot between them intended for guiding the windpipe and gullet when the set of plates is moved along the front side of the carcass, or may be intended to be moved from above. However, in a preferred embodiment the holding members of the holding device can be moved between a first position, in which they allow the plucks set to pass between them, and a second position, in which they allow only the windpipe and gullet to pass be¬ tween them. Thereby the holding members, which are preferably plate-like, can be interposed between the carcass and the plucks set one from each side. As the movement of the holding members may then take place substantially without vertical movement, this embodi- ment is particularly advantageous in case of lack of space or to give room for other equipment. Depending on the design of the holding device the pull that can be exerted on the windpipe and gul¬ let may not be sufficient or may not have the correct orientation. The apparatus may therefore comprises clamping means, which may clamp the windpipe and the gullet, the larynx or the connections between the larynx and the tongue, thereby securing the plucks set and allowing a contribution to or replacement of the pull of the holding device either in the same or in a different direction. The clamping means prefera¬ bly function independently of the holding device to allow them to be employed simultaneously or individu¬ ally as required. In some cases the pull exerted on the windpipe and gullet by the holding device and clamping means is sufficient to loosen the windpipe and gullet suf¬ ficiently from the inside of the carcass to allow the cutting means to work. An incomplete separation may, however, inhibit the optimal insertion of the neces¬ sary tools and it is therefore preferred that the ap¬ paratus comprises a stamper, which is designed for loosening the windpipe and gullet from the carcass, and means for moving the stamper upwards and down- wards in an alternating manner. The movement of the stamper causes the connections of the windpipe and gullet to the inside of the carcass to be torn. The use of a stamper in stead of e.g. a knife is advanta- geous as the membranes etc. constituting the connec¬ tions are often soft and elastic and as they are lo¬ cated in places, where cutting would involve a con¬ siderable risk of damaging the surrounding tissue. When using a positioning device as described above it is important to know the position of the choanae in the carcass . During other processes on pig slaughter lines the distance between the point from which the carcass is hung by the hind legs and the point where the front legs meet the body, is often measured. However, due to anatomical difference be¬ tween pigs this measure cannot be use for determining the position of the choanae with sufficient preci¬ sion. In a particularly preferred embodiment the stamper is therefore designed to come into direct or indirect abutment against one or more parts of the carcass inside the head of the carcass, preferably against processus paracondylaris, which are bones projecting from the cranium closely behind the jaw- joint. When a firm point has been localised by means of the stamper, the positioning device can be in¬ serted very precisely. Other tools for processing of the carcass can be positioned for operation using the localisation of the firm point. The object of the invention is further achieved by a method, where the larynx is loosened from the inside of the carcass by means of a cutting means, which is moved downwards in a substantially vertical direction, so that the larynx is loosened from the head but stays connected to the plucks set. By this cut at the larynx the plucks set is loosened. By cuts at the tongue, the plucks set can then be free from the carcass without cutting the windpipe and gullet and without contamination with bacteria from the ton¬ sil . In addition the loosening and removal method may be automated completely or partially, thereby reduc¬ ing or superseding manual labour. In a preferred embodiment the cutting means is positioned using a positioning device, having two pointed projections, which are arranged one in each of the choanae. This method in particular contributes to increasing the precision of cutting. Further, it is preferred that the cutting is performed by moving a knife of the cutting means downwards with the cutting edge of the knife in front thereby loosening the larynx on the side facing the spine. For this a knife blade having an edge, which curves around an axis substantially parallel to the intended direction of movement of the knife or which has more than one curved parts with different radii of curvature and possibly curves around different axes, is preferably used. This method achieves a safe loosening where the risk of damaging the different parts of the carcass is minimised. In a still more preferred embodiment the con¬ nections of the windpipe and gullet to the inside of the carcass is loosened by means of a stamper, which is moved upwards and downwards in relation to car¬ cass. The upwards and downwards movement of the stamper may be continued until the stamper comes into direct or indirect abutment against one or more parts of the carcass inside the head of the carcass, pref- erably against processus paracondylaris. Hereby the access of tools is facilitated and in addition a se¬ cure fixation of the head is achieved. During the above operations a pull is prefera- bly exerted on the windpipe and the gullet away from the carcass by means of a holding device having two holding members, which are moved between a first po¬ sition, in which they allow the plucks set to pass between them, and a second position, in which they allow only the windpipe and gullet to pass between them. The pull of the holding device may be supple¬ mented or replaced by the use of clamping means, which clamp the windpipe and the gullet, the larynx or the connections between the larynx and the tongue. In the following the invention will be ex¬ plained in more detail based on the embodiments shown in the drawing. Fig. 1 is a side view of part of an apparatus for loosening a plucks set from a pig carcass hung from the hind legs with the plucks set held by a holding device, Fig. 2 is a perspective view showing the hold¬ ing device holding the plucks set, Fig. 3 is a perspective view showing a clamping device for clamping the connection between the larynx and the tongue, Fig. 4a shows a stamper and dilating device seen from the side, Fig. 4b shown the head of the stamper in Fig. 4a, Fig. 5 shows a horizontal cross section of the carcass as indicated with the line V-V in Fig. 1 seen from above where the stamper and the dilating device are arranged therein, Fig. 6 shows a pig cranium seen from the spine, Fig. 7 shows a pig cranium in cross sectional view along a centre plane being substantially aligned with the spine, Figs. 8 and 9 shows en embodiment of a cutting device for cutting the larynx loose seen in perspec¬ tive views from two different angles, and Fig. 10 is a cross section through the lower¬ most part of a pig carcass hung by the hind legs with parts of the apparatus for loosening the plucks set. In the description below the apparatus is used on a pig carcass 1, which is hung by the hind legs 2 as shown in Fig. 1 and where the abdominal cavity has been cleared. Viscera and several of the internal or¬ gans have been removed so that only the heart plucks set 3 comprising heart and lungs are left . The appa¬ ratus may, however, also be used on carcasses where all or more of the internal organs and possibly the viscera are left in the plucks set. The plucks set hangs by the windpipe and gullet 4 through the inci¬ sion made in part of the throat, the chest and the abdomen. The carcass 1 is held by means of shackles 5 arranged around the forelegs 6 and which pulls the carcass backwards so that the back is pressed against an abutment 8. The pull of the shackles on the fore¬ legs causes the carcass to be opened at the incision in the abdomen, chest and throat. Further, the head of the carcass is secured by means of a vertically operating, self-positioning forehead rest 7, which adjust to the anatomy of the carcass. A holding device 20 exerts a pull on the wind- pipe and the gullet 4 as indicated by the arrow A in Fig. 1. The pull of the holding device causes part of the connections of the windpipe and gullet to the in¬ terior of the carcass 1 to be torn and the rest to be stretched thereby making room all the way down to the larynx 9. To secure the carcass 1 a retainer 10 may be arranged around the lower part of the carcass as shown in Fig. 1. As shown in Fig. 2 the holding device comprises two plate members 21a,21b, each of which may pivot about an axis 22a,22b as shown by the arrows B thereby bringing them closer to or further away from each other, the latter being shown by the arrows C. When having to catch a plucks set 3 hanging down the front of a carcass 1 the plate members 21, in their position furthest apart, are moved towards the carcass and arranged one on each side of the plucks set close to the carcass 1 (not shown) . The plate members are then brought closer together thereby being interposed between the carcass and the plucks set . When the plate members have reached the position shown in the Fig. 2, the plucks set can no longer pass between them and when the holding device 20 is then pulled away form the carcass the plucks set abuts against the back side of the plate members as seen in Figs. 1 and 2, whereby a gradually larger pull is exerted on the windpipe and gullet 4. To keep the plate members 21 from damaging the plucks set, the edges facing it is provided with edge plates 23, only one of which can be seen in Figs. 1 and 2. Further, the curved cross sectional shape of the plate members 21, seen particularly well in Fig. 1, is intended to give room for the different organs of the plucks set. It may therefore be necessary to adapt the shape of the plate members if the apparatus is to be used for loosening different types of plucks set, e.g. making them bigger if the plucks set in¬ clude more different parts. When the windpipe and gullet 4 connecting the plucks set 3 to the carcass 1 are under tension, the plucks set is held at the upper part of the holding device as shown in Fig. I7 but when the connection is broken or the pull weakened the plucks set will be lowered by gravity. To avoid the plucks set being dropped or hanging to low, the lower parts of the plate members have a hook shaped cross section so that their outermost parts 24 form a collection sur¬ face or tray. It is to be noted that other designs of the holding device such as the one mentioned in the Dan- ish patent mentioned above may also be used. The pull exerted by means of the holding device 20 may not be sufficient to break the connections in the carcass or it may not be possible to give the right direction to the pull . In such cases a clamping device 30, as the one shown in Fig. 3, may be pro¬ vided. In the embodiment shown, the clamping device comprises two curved members 31,32 intended to clamp around the connection between the larynx and the tongue (not shown) . One curved member 31 being sta- tionary, while the other 32 can pivot as indicated by the arrow D and has a projection 33 for enabling a better grip. After clamping, the device 30 is moved away from the carcass to tear connections in the car¬ cass. To bring about a further loosening and opening behind the larynx 9, a stamper 40 as the one shown in Figs. 4a and 4b is inserted through the incision in the abdomen, chest and throat as shown in Fig. 5. The stamper is moved upwards and downwards in a pulsating manner whereby it causes tearing of connections not torn by the pull on the windpipe and gullet 4. In the embodiment shown, the entire arm 41 of the stamper is moved up and down, but the arm may also be provided with a joint (not shown) allowing a separate movement of the front part or head 42 of the stamper. The head 42 of the stamper is preferably shaped as shown in Fig. 4b, having two downward directed projections 43. The projections are separated by both a vertical slot 44 in the front and a horizontal slot 45 in the underside of the stamper head 42. This de¬ signs allows a particularly good contact with the tissue and bone inside a pig head and may of cause be adapted for the use of the invention on other species of animal such as cattle. Stampening is continued until the stamper 40 comes into abutment against the projecting bones processus paracondylaris 11, which is located on the cranium close to its connection to the spine. See Figs. 6 and 7. The abutment of the stamper against firm parts of the head has the advantage that the precise position of the different parts of the head and throat can then be determined with a relatively close accuracy. When the stamper 40 is in its end position it further contributes to a particularly effective fixa¬ tion of the head, after which a not shown apparatus, which is integrated in the present design, may per- form a cutting of the jowls where meat is detached from the cheeks and jaw. Cf. e.g. Danish patent ap¬ plication PA 2000 00459 (Slagteriernes Forskningsin- stitut) and Danish patent application PA 2005 XXXXX filed simultaneously with the present application. Fig. 5 shows a horizontal cross section of the carcass where the stamper is • in its end position and further shows how a dilating device 50 may be used for improving the conditions of access to the inte¬ rior of the carcass. The dilating device, which is seen from the side in Fig. 4a, comprises two spoon- like dilating members 51 designed for contacting the tissue 52 on the two sides of the incision in the carcass. When introduced into the carcass the dilat¬ ing members 51 are substantially parallel and when the members are in place within the carcass they are swung away from each other as indicated by the arrows E in Fig. 5, the dilating members pivoting around axes 53 and 54. In the embodiment shown in Figs. 4a the stamper and dilating device are integrated but two separate devices may of cause be used with similar result or the dilating device may be left out. The stamper and dilating device are withdrawn from the carcass and a cutting tool 60 as illustrated in Figs. 8 and 9 is inserted as shown in Fig. 10, the cutting tool being used for cutting the larynx 9 from the backside of the throat. The insertion is prefera- bly performed by a substantially curved movement as indicated by the arrow F in Fig. 10, whereby the tool comes into contact with the back 12. When this con¬ tact is established the tool is placed as far back in the carcass as possible and in a relatively well- defined position. During the last part of the inser¬ tion two projections 61 of a positioning member 62 is directed into the choanae 14 as may be seen in Fig. 10. A position immediately above the larynx at the backwards-facing opening of the nasal cavity 15. Hereby the cutting device 64 of the cutting tool is placed in a very well defined position in relation to the cranium and thus also in relation to the other parts of the head and the throat . The design of the positioning device 62 is shown most clearly in Fig. 8. As may be seen, the projections 61 are rounded on the side 63 facing the back 12 during use. This rounding reduces the risk of the projections 61 getting caught when the device comes into contact with the back during the insertion in the carcass. The insertion of the cutting tool 60 must be very precise as there is not much room. If it goes to fare back the projections 61 of the positioning mem¬ ber will be caught by the bones and cartilage of the back 12 and if it is not inserted deep enough the projections will cause damage to the larynx 9. The projections 61 may of cause be of a less pointed de- sign than what is shown in Figs. 8 and 9 whereby the risk of such damage is reduced. However, the points of the embodiment shown contribute to the penetration of membranes often covering the access to the cho- anae. The larynx is cut partially loose by means of the cutting device 64, which is most clearly shown in Fig. 9. In Fig. 8 the cutting device is located hid¬ den in the positioning device 62. The cutting device and the positioning device, together forming the cut- ting tool 60, are inserted simultaneously. The cut¬ ting device may, however, also be inserted separately following the insertion of the positioning device. In the embodiment shown the cutting device 64 is designed to be passed down along the backside of the throat as indicated by the arrow G during the separation of the larynx there from. As may be seen, the cutting device is very close to the tonsils 17, which illustrates the importance of a precise posi¬ tioning. If the tonsils, which contain a lot of bac¬ teria, come into contact with the cutting device it may lead to a contamination of the meat. For the same reason it is important that the pull on the windpipe and gullet 4', 4' 1 is such that it will not cause the tonsils 17 to be forced against the cutting device 64. As may be seen from Fig. 9, the cutting device is a chisel-like knife, the edge of which is composed of three curved sections 65,66,67. The two outermost sections 65,67 have the same radius and axis of cur¬ vature while the third and midmost section 66 has a smaller radius of curvature and an axis of curvature, which is advanced in relation to axis of the utter- most sections so that the midmost section projects over the two outermost sections. In this embodiment the cross sectional shape of the knife corresponds to the shape of the underside 16 of the cranium as shown in Fig. 6. This eases the passing forward of the cut- ting device in that the risk of it e.g. hitting on protruding projections 18 of the cranium is reduced. Furthermore a close cut is obtained. As mentioned above and shown in Figs. 8 and 9, the cutting device 64 is located within the position- ing device 62 both being partly tubular. Conse¬ quently, the direction of passing forward the cutting device is substantially parallel to the common length axis. When the positioning device is placed in the choanae 14 there must, as may be seen in Figs. 6 and 9, be a distance d between it and the knife to enable the latter to stear clear of the underside of the cranium as described above. Therefore the projections 61 of the positioning device 62 are offset in rela¬ tion to the pipe of which it is constructed. Depending on e.g. size variations between slaughter animals, racial variations etc. other suit¬ able designs may of cause be possible. For example designs having a different relationship between the radii of curvature of the knife and the distance be¬ tween the axes of curvature may be imagined. Further¬ more, particularly if the apparatus is to be used for other species of animals such as cattle, different geometries with more or less sections may be prefer¬ able. Finally, it may be seen from Fig. 9 that the cutting device 64 in the embodiment shown has a de¬ sign where the knife blade 68 curves in several planes. This contributes to easing the passing for¬ ward of the knife through the tissue. The larynx has now been cut partially loose from the carcass, but to disengage the plucks set completely it must also be cut loose along the sides and on the front side underneath the tongue 19. This is preferably done using three cuts. These may be performed manually or automatically e.g. by the use of three different knifes of a cutting arrangement . For cutting along the sides a traditionally designed knife may be used, possibly having a curved edge, or alternatively a device having an oscillation cutting edge as is known from e.g. the meat industry. The un¬ dercutting of the tongue may advantageously be per- formed using a knife, which is pushed forward corre¬ sponding to the one described above, but a regular or oscillation knife may also be used. In the above the invention has been described for use for removal of a plucks set comprising tongue, larynx, windpipe, gullet, heart and lungs. It is, however, to be understood that the invention may also be used for the removal of other types of plucks sets from the carcass . Pneumatic or hydraulic cylinders or other driv¬ ing devices may be used for moving the tools, de¬ vices, knifes etc. mentioned above. A control device controls the operation of these driving devices, so that a processing program resulting in the above functions for loosening the plucks set is carried out for each carcass. Additionally, it is to be understood that dif¬ ferent features of the embodiments shown may be left out or combined in a number of other ways than what have been described in the above without causing such embodiments to fall outside the scope of the claims.