referring to the drawings wherein like reference characters designate like or corresponding parts throughout the several views , and referring particularly to the prior art devices of fig1 and 2 , it is seen that the artificial insemination gun , used particularly for bovines , comprises a tubular body 54 provided at one end with a head 52 for fixing a sheath and terminating in an annular flange 50 that is held in the technician &# 39 ; s fingers . adjacent to its other end , body 54 has a counterbore defining an inner shoulder against which bears one end of a supply of semen or straw 63 provided with a piston - plug 60 . body 54 further comprises a plunger - rod 53 which is slidably mounted in the body so as to be capable of shifting by an end thereof the piston - plug 60 and consequently ejecting the semen contained in the straw 63 . at its other end , the plunger - rod 53 has a flange 50 for pushing when dislodging semen . body 54 and the plunger - rod 53 are , for example , made from stainless steel . the gun is completed by a cylindrical breeding sheath 70 which slides over and covers the whole of the body 54 and the straw 63 . the straw 63 bears by its front end against the inner surface of a convergent portion 72 of this sheath which has an ejection orifice 74 . at its other end , the sheath is elastically clamped against a flared frustoconical portion of the head 52 by means of a clamping or “ o ” ring 64 . the semen straws are crimp sealed on one end , and the crimped end of the straw is removed before use , creating an opening 61 through which the semen can be expelled . sheath 70 is disposable , and is employed for each insemination operation and is slipped over the gun before its insertion into the reproductive passages of the animal . the sheath 70 is discarded once the apparatus has been withdrawn from the animal , so that the gun body 54 is not soiled and may be again employed without inconvenience on another animal after having been covered with another sheath . once the straw 63 is in place , the sheath 70 is slid over the artificial insemination gun body 54 and the semen straw . the sheath is made of a thin plastic material that is of slightly larger diameter than the body 54 of the insemination gun . when the open end of the semen straw 61 reaches the convergent portion of the sheath 72 , a snug and / or airtight fit is accomplished and creates a seal with the convergent portion of the sheath 72 . this seal is maintained by a locking ring which is slid over the sheath 70 , and is of a diameter just slightly larger than a portion of the base of the sheath , as to allow the locking ring 64 to be manually secured on the sheath by applying downward force on the ring 64 . once secured , the semen straw 63 is secured in place as the tip of the sheath 72 narrows in diameter creating a lip or edge preventing the semen straw from exiting the sheath . after securing the sheath 70 in the prior art embodiment of fig1 and 2 , a protective or outer sheath 80 may then be placed over the inner sheath 70 . the outer sheath 80 is made of a thicker plastic material and is of a diameter large enough that it fits loosely over the inner sheath 70 . the outer sheath 80 is shorter in length than the inner sheath 70 . the tip of the prior art outer sheath 80 is covered by a rubberized cap 82 . the rubberized cap 82 has slits 84 , usually formed in an “ x ” pattern , which allow the inner sheath 70 to be extended though the tip 82 by applying downward pressure on the flared edge 86 of outer sheath 80 with respect to the inner sheath 70 and the rest of the insemination gun apparatus 54 . the outer sheath 80 and cap 82 are intended to cover the inner sheath 70 while the insemination gun assembly 54 is traveling through the vagina where contaminants might otherwise enter through opening 74 in sheath 70 . fig1 is a schematic view of the components of the artificial gun assembly of the prior art insemination device . fig2 depicts an embodiment of the prior art artificial insemination sheath in an assembled state . as shown , the outer sheath 80 is of a shorter length than the inner sheath 70 . the end of the outer sheath has slits 84 , but remains in a closed position while resting on the end of the tip of the inner sheath . 70 . once the device is inserted to the base of the cervix of the animal the breeder applies downward pressure on the flared section 86 of the outer sheath to force the tip 72 of the inner sheath 70 through the slits 84 of the rubber tip 82 of the outer sheath 80 . the outer sheath can then slide downward until the flared section 86 comes in contact with the locking ring 64 . this gives the breeder a section of the inner sheath , which is thinner , to insert into the cervix of the animal , before hitting the rubberized tip 82 of the outer sheath . this also allows the breeder to expel the semen as the upper opening 61 of the semen straw 63 corresponds to the opening 74 at the end of the inner sheath 70 and is no longer covered by the rubberized tip 84 . fig3 is a cross sectional view of one embodiment of the prior art apparatus . it shows the relative diameter of each individual component part . comparing to fig6 , which is a cross - sectional view of one embodiment of the present invention , it is noteworthy that the diameter of the present invention is the same as that of the inner sheath of the prior art invention of fig1 - 3 . fig4 is a schematic view of one embodiment of the present invention . the present invention relates to an improved sheath 70 , which slidably fits over a standard artificial insemination gun assembly 54 . a semen straw 63 is inserted into the artificial insemination gun at the distal end 51 in the same manner as previously discussed in the prior art invention . in addition , the sheath 70 is then slid over the loaded artificial insemination gun and secured using ring 64 in the same manner as the prior art sheath . fig5 shows an assembled gun apparatus of the present invention including a sheath 70 with covering 102 over the opening 74 at the tip . as shown in the cross - sectional view of fig6 , the tip 72 of the sheath 70 is tapered , narrowing to a smaller diameter . tip 72 may have a frustoconical shape . the smaller diameter is less than that of the diameter of the semen straw 63 which is enclosed between the gun end 51 and the tip 72 of the sheath 70 ( see detail of fig1 ). the opening 74 at the tip of the sheath is sealed by a coating 102 . in the illustrated embodiment , coating 102 not only completely covers opening 74 but may also extend a distance down the tapered side of tip 72 to ensure that the tip is completely enclosed . in other embodiments , coating seal 102 may be provided in the form of a thin plug on the inside of tip 72 to prevent materials from passing through opening 74 . fig7 is a cross sectional view of the artificial insemination gun of the present apparatus inserted in the vagina of a bovine . the figure depicts the basic structure of the reproductive tract of a bovine or other livestock . the animal has an anus 200 at the end of the animal &# 39 ; s intestinal tract 205 . with regard to bovines and other large livestock , the breeder inserts a hand through the anus 200 and into the intestinal tract 205 of the animal . the walls of the intestinal tract of the animal are thin and elastic allowing the breeder to feel and manipulate portions of the reproductive system through the wall of the intestines . the reproductive system of livestock , particularly a bovine , consists of a vagina 140 which extends a distance into the animal to the internal reproductive bodies . the vagina 140 extends to the cervix 144 . in general , the cervix is more narrow and rigid than the vagina . the cervix has cervical rings 145 making passage through the cervix 144 difficult . at the end of the vagina 140 , there are blind pouches 147 , where the vaginal body extends slightly past the opening to the cervix 144 . often times the blind pouches can present an obstacle to the breeder in attempting to insert the artificial insemination gun into the cervix 144 . at the end of the cervix is the uterine body 148 . the rate of pregnancy is highest when sperm - containing semen is injected as close as possible to the uterine body 148 . fig8 is a cross sectional view of the apparatus of the present invention in the process of injecting semen near the uterine body 148 . the coating 102 of the sheath 70 is ruptured through the application of pressure transferred from the manual force of the user on the plunger flange 50 to the seminal fluid in the semen straw . the pressure on the coating 102 , causes this surface to rupture allowing for the semen in the semen straw 63 to exit . a skilled breeder can cause this to occur as close as possible to the uterine body 148 . to ensure that the semen is properly dispensed , the plunger should be depressed in a slow steady motion . fig9 is a view of an embodiment of the covered tip of the sheath of the present invention . the tip 72 of the sheath 70 narrows in diameter before becoming an opening 74 . the opening is sealed by a covering 102 . in this illustrated example , the covering encloses the opening 74 and extends a distance down the side of the sheath to ensure the opening 74 is fully sealed . the coating 102 is made of a thin material as to not greatly increase the diameter of the tip 72 of the sheath , to ensure easy insertion of the artificial insemination device . fig1 and 11 are cross sectional views of an embodiment of the artificial insemination sheath of the present invention . fig1 depicts the invention with the coating 102 intact , and fig1 shows the covering ruptured to allow for the expulsion of the semen . the drawing depicts portions of the artificial gun assembly 54 . as shown , the sheath 70 covers the shaft 51 of the artificial insemination gun . the semen straw 63 fits within the shaft 51 . the tip of the semen straw 63 is pressed against the inside of tip 72 of the sheath , preventing further movement . the semen straw 63 while placed in the shaft 51 of the artificial insemination gun extends a distance beyond the end of shaft 51 . the plunger mechanism 53 can be manually extended through the semen straw 63 to eject the semen contained in the straw . as shown , the rupture 103 of the coating 102 is minimal . the coating when ruptured , tears in a manner that it does not create fragments which could be left in the reproductive cavity . in addition , the coating has enough adhesive strength to remain attached to the tip of the sheath even when pressure is applied to plunger mechanism . in one embodiment , the coating is applied by dipping the very end of the sheath into a fluid polymer solution so that the polymer adheres to the tip of the sheath . the sheath ( or group of sheaths , for mass production ) is oriented in a vertical direction with the pointed tip facing downward . the end of this tip is moved in a downward direction and dipped into an open reservoir of the solution so that some of the solution adheres to the tip . it is then removed with an upward movement and taken aside to cure . depending on the material used , this could take about 15 minutes . in some embodiments , the sheath may be rotated while the tip is in the solution , or immediately following the removal of the dipped tip from the solution , in order to assure even distribution of the coating on the tip . after a brief time , which may be before the material has fully cured , the sheath with its dipped tip may be moved to a non - vertical position for drying , further curing , and eventually for packaging and shipment . it is preferred that the dipping , curing and packaging operations be conducted in a sterile or semi - sterile environment , so that the coated sheaths may be delivered in such condition for use by the technician . in other embodiments , the coating may be applied to the sheath tip by wiping or painting using a sponge , brush or other suitable applicator . in one embodiment , the coating may be provided as an integral part of the sheath when it is manufactured . in this embodiment , instead of providing a sheath that is open at both ends , the opening at the narrow frustoconical end is closed using a very thin layer of the same material that the sheath is made of . this layer must be thin enough to be ruptured by the normal pressure applied by the insemination gun and plunger . in another embodiment , a pre - scored area ( such as a line or “ x ”) or a tiny pin hole may be provided in the coating . the pre - scored or thinner area provides a weakened portion that is easily ruptured with the normal pressure applied by the insemination gun and plunger . similarly , the pin hole provides a starting point for rupturing the coating using the normal pressure applied by the insemination gun and plunger . it is to be appreciated that although some small amount of contamination may enter thorough the pin - hole , this small amount could be easily expelled in the cervix before the tip reaches the uterine body using the pre - rupture method described previously . it is to be appreciated that different versions of the invention may be made from different combinations of the various features described above . in particular , any number of light weight elastic materials can be used to make the coating to the sheath 102 . it is to be understood that other variations and modifications of the present invention may be made without departing from the scope thereof . it is also to be understood that the present invention is not to be limited by the specific embodiments disclosed herein , but only in accordance with the appended claims when read in light of the foregoing specification .