each other and have a tubular shape with a diameter which is substantially greater than the diameter of one of the secondary conduits 3 the bridges of material 9 connect the adjacent ends of the segments 5 to 8 and have a small width so that they can undergo a certain flexion making it possible to orient these segments in relation to one another in particular the segment 6 in relation to the segment 7 the device 1 is made by appropriate cutting of a sheet of nickel titanium alloy known by the name nitinol then folding the resulting blank into a circle and welding the parts of this blank which come into proximity with each other this alloy is malleable at a temperature of the order of 10 u00b0 c but can recover its neutral shape at a temperature substantially corresponding to that of the human body fig2 shows the device 1 in a state of radial contraction obtained by cooling its constituent material during this contraction the edges 10 a pivot in relation to the transverse edges 10 b of the meshes 10 in such a way that the meshes 10 have in this sate of contraction a substantially rectangular shape by virtue of this contraction the segments 5 to 8 have a cross section which is smaller than that of the conduits 2 and 3 and they can be introduced into these as will be described hereinafter the device 1 is engaged on a central support core 15 and is then contracted radially on the latter this core 15 comprises an axial abutment such as a shoulder not visible in fig2 which has a diameter smaller than.