referring to the fig1 - 3 , one embodiment of the present invention consisting of a prophylactic device 10 comprising a collapsible tube 12 formed with a thin impermeable elastic material is shown . latex rubber with a thickness of approximately 0 . 002 inches is a suitable substance . the collapsible tube 12 includes an open end 14 , a closed end 16 and a midsection 18 . the midsection 18 is formed with a plurality of fanfolds or pleats 20 . the pleats 20 are shown in their collapsed state in fig1 and in their expanded state in fig3 . each pleat 20 is formed by two opposed and opposite frusto - conical sections 19 . with all the pleats fully extended , the prophylactic device 10 has a maximum length of approximately twice the length of an erect mature male penis , p . in practice a suitable length is seven to fourteen inches . the midsection 18 has a relaxed diameter 21 substantially equal to or greater than the diameter of the erect mature male penis , p . in practice a suitable relaxed diameter is one to two inches . a conventional lubricant ( not shown ) is provided on the inner wall of the device . the midsection 18 has an outer wall 23 and an inner wall 24 . the open end 14 consists of a truncated conical section 26 . the truncated conical section 26 has a minimum diameter 28 slightly less than the diameter of the mature male penis , p . the truncated conical section 26 includes a rolled lip 30 . an optional adhesive band 31 may be included in the truncated conical section 26 and covered with a peel - away liner 32 having a liner pull tab 33 . in operation , the mature male penis , p , is inserted into the prophylactic device 10 . the truncated conical section 26 forms a seal around the base of the penis 22 . the truncated conical section 26 fits tightly around the base of the penis 22 as the truncated conical section 26 minimum diameter 28 is forced to expand to an enlarged diameter 29 by the slightly larger diameter mature male penis , p . the thin impermeable elastic material urges the truncated conical section 26 back to its original diameter 28 thereby affixing and sealing the prophylactic device 10 to the base of the penis , p . an adhesive band 31 may also be used to affix the prophylactic deivce 10 to the base of the penis , p . once the penis is inserted in the prophylactic device the peel - away liner 32 may be removed with the liner pull tab 33 . referring to fig2 after the penis , p , is inserted into the vagina , v , during withdrawl , the lubricant in the prophylactic device 10 allows the penis , p , to move relative to the prophylactic device 10 while the prophylactic device 10 remains seated in the vagina , v . as depicted in fig2 and 3 , the pleats 20 which extend in accordian - like fashion along the length of the midsection 18 , allow the collapsible tube 12 to expand and contract as the penis moves within the vagina and the prophylactic device 10 , while the prophylactic device 10 remains approximately stationary with respect to the vagina , v . a second embodiment of the present invention , characterized by an inwardly folded sleeve section , is shown in fig4 a , 4b and 4c , and with modifications in fig5 a , 5b and 5c in fig6 a and 6b . the second embodiment is shown fitted on an erect male penis before insertion into the vagina in fig4 a , after insertion in fig4 b , and after withdrawal in fig4 c . with reference to fig4 a , 4b , and 4c prophylactic device 40 has an open end 41 , a closed end 42 , a midsection 43 , and a truncated section 44 . a cylindrical sleeve 45 , integrally formed from the sheet material that forms prophylactic 40 , is folded inwardly at opening 41 . four relatively rigid thin plastic discs 46 are adhered to the outwardly facing surface of sleeve 45 as shown . rigid discs 46 serve to prevent sleeve 45 from being rolled over on itself , thereby lowering the resistance to removal of prophylactic 40 from penis , p , in a manner described more particularly below . the embodiment of fig4 a , 4b and 4c is formed of impermeable thin sheet material , as is well known in the art , and has the following typical dimensions , which achieve the desired results with a typical erect male penis . the overall length of the prophylactic 40 from open end 41 to closed end 42 is four to five inches . the diameter of mid - section 43 is one and one - half to one and three - fourths inches . the diameter of opening 41 is one to one and one - half inches . the altitude of truncated section 44 is about three - fourths inch and the diameter of discs 46 is about three - sixteenths inch , with sleeve 45 about one - fourth inch in altitude or height . in general , the dimensions of prophylactic 40 are chosen so that there is a snug , sealing fit of sleeve 45 around the shaft of penis , p , and a loose fit of midsection 43 about penis , p , including the glans thereof , to achieve the requisite relative movement of the penis , p , with respect to the wall of midsection 43 of prophylactic 40 during copulation , responsive to the long - felt need in the art . the specific dimensions may vary from those specified to achieve the desired result . in use , the embodiment of fig4 a , 4b and 4c is fitted onto an erect male penis , p , as shown in fig4 a . sleeve section 45 is positioned on the shaft of penis , p , so as to leave a substantial distance from the tip of penis , p , to the closed end 42 of prophylactic device 40 . when penis , p , and prophylactic 40 are inserted into the vagina in use , penis , p , moves into engagement with closed end 42 as truncated section 44 rolls over itself , and the portion of penis , p , from sleeve section 45 to the tip thereof moves relative to the wall of midsection 43 of prophylactic device 40 . the limits of this movement are shown in fig4 a and 4b . in moving from the position of fig4 b to the position of fig4 c there is some tendency , because of frictional forces , to pull prophylactic 40 off penis , p . this result is extremely undesirable and to insure that it does not occur rigid discs 46 are adhered to the outwardly facing wall of sleeve 45 . in the absence of discs 46 , the thin flexible sheet material that forms phrophylactic 40 can fold or peel over itself beginning at the fold at opening 41 and extending through the height of sleeve 45 , thereby peeling sleeve 45 from its position as prophylactic 40 is pulled off penis , p . rigid discs 46 prevent the folding over on itself or peeling of sleeve 45 in that when the fold line in sleeve 45 reaches the periphery of discs 46 , further pulling requires a tilting or lifting up of the edge of discs 46 in order to continue with the peeling process . this is shown in somewhat exaggerated form in fig4 c in which discs 46 are shown fitting outwardly at the point of engagement with the fold at opening 41 . discs 46 are prevented from flipping over by the resiliency or lack thereof of the sheet material that forms prophylactic 40 . consequently , discs 46 prevent further folding over on itself or peeling of sleeve 45 . this means that sleeve 45 can be pulled off only by overcoming the frictional force at the interface with penis , p , and this frictional force is sufficient to prevent removal of prophylactic device 40 . thus , in use , prophylactic device 40 provides for movement of penis , p , with respect to the wall of midsection 43 , back and forth , between the positions of fig4 b and the position of fig4 c . this more closely simulates copulation without any barrier or prophylactic device and , at the same time , provides for a secure , reliable seal or protective barrier betweeen partners for birth control purposes and to prevent the transmission of disease . a modification of the embodiment of fig4 a , 4b and 4c is shown in fig5 a , 5b and 5c . with reference to fig5 a and 5b , prophylactic device 50 includes an open end 51 , a closed end 52 , a midsection 53 , an intermediate truncated section 54 , a double ply sleeve section 55 , a neck section 56 and a terminal truncated section 57 . the size , configuration and functioning of the modified design of fig5 a , 5b and 5c is similar to that of the embodiment of fig4 a , 4b and 4c , except that the modification of fig5 a , 5b and 5c has a welded two - ply sleeve section , no rigid disc structure , an extended neck section 56 and a flared or truncated terminal section 57 . with the modified design of fig5 a , 5b and 5c , relative movement between penis , p , and midsection 53 of prophylactic device 50 occurs as shown in fig5 a , 5b and 5c . pulling off of prophylactic device 50 from penis , p , is prevented by the double - ply , extra resiliency or strength in sleeve 55 and the increased frictional force due to the increased area of snug engagement with the shaft of penis , p , extending through neck section 56 . this is best seen in fig5 c in which the double - ply construction of sleeve 55 can be seen to resist at edge 58 peeling of double - ply sleeve section 55 , aided by neck section 56 . in the modification shown in fig6 a and 6b , prophylactic device 60 includes an open end 61 , a closed end 62 , a midsection 63 , which is pleated or folded over on itself , and a truncated sleeve section 64 . truncated sleeve section 64 includes a welded , two - ply portion near opening 61 and a single - ply portion to which two rigid tabs 65 are adhered . tabs 65 function in the same manner as discs 46 in prophylactic device 40 in preventing the unwanted removal or peeling - off of prophylactic device 60 during use . thus , truncated sleeve 64 combines the features of the embodiment of fig4 a and 4b and the modification of fig5 a and 5b in that both a rigid tab structure and a double - ply sleeve structure is provided to prevent unwanted removal of the prophylactic device 60 . in each of the designs of fig4 a , 4b and 4c ; 5a , 5b and 5c and 6a and 6b , a lubricant can be provided inside the prophylactic device ; however , lubrication on the snugly fitting portion of the device that engages the shaft of the penis is not desirable . to confine lubication to only that portion of the device in which relative movement of the penis with respect to the device is desired , a breakable seal can be provided at the inside terminal edge of sleeve section 45 ( in a flattened state ) in the design of fig4 a , 4b , and 4c at the inside terminal edge of sleeve 55 in the design of fig5 a , 5b and 5c , and at the inside terminal edge of truncated sleeve 64 in the design of fig6 a and 6b , after lubricant has been applied to the inner - wall , midsection area of the respective devices . the seal is broken when the device is applied for use . unlike prior prophylactic devices , the present invention thus provides for relative movement between the penis and the prophylactic device and direct frictional stimulation of the penis on both the insertion stroke and the withdrawal stroke , thereby simulating copulation without a prophylactic device , while retaining the disease prevention and birth control functions of the prior art devices .