WO 01/43626 PCT/AUOO/01526 ANAL SPECULUM Technical Field This invention relates to anal speculums for use by 5 surgeons in the treatment of haemorrhoids. Background art Prior known speculums for that purpose have comprised a tubular probe, for insertion into the anus, wherein a hole pierces the tube wall of the probe near its- front or leading 10 end. When using those prior known speculums a surgeon had to align the probe, before insertion, with a haemorrhoid to be treated and then insert the probe to a depth enabling access through the hole to the haemorrhoid in question. This has been an awkward procedure and requires retraction and 15 reinsertion of the probe one or more times in the event that one or more further haemorrhoids require to be treated at the one treatment session. This is objectionable not only for the surgeon, because of the difficulty in correctly aligning and inserting the probe and working with limited access to 20 the, or each haemorrhoid, but also for the patient, because each insertion is accompanied by a degree of discomfort, if not actual pain. 1 WO 01/43626 PCT/AUOO/01526 Disclosure of invention An object of the invention is to alleviate the objectionable features of the prior art speculums referred to above. 5 The invention consists in an anal speculum of the kind comprising a tubular probe adapted to be inserted into the anus of a patient, characterised in that a leading end face of the tubular probe has two or more bights formed therein. In preferred embodiments there are three such bights 10 equiangularly spaced apart and dimensioned such that the open mouths of the bights together constitute at least 50% of the circumference of the leading end face of the probe. Thus, when a said preferred embodiment is used, frequently a single insertion will suffice, and at most no more than two 15 insertions are needed, to pick up all of a patient's haemorrhoids for treatment. For preference each such bight may be tapered to some extent, such that its side edges converge from a widest portion at the mouth of the bight. 20 When the bights are tapered as aforesaid and the probe is inserted, any haemorrhoid or swollen vein needing treatment within the ambit of the wide open, leading end of any bight is guided by one or other or both side edges of the bight to 2 WO 01/43626 PCT/AUOO/01526 a position at or near the narrower trailing end of the bight, where it may be treated by injection or ligation. For preference the probe is a disposable item, able to be easily fixed to a conventional handle. The probe may thus be 5 discarded after a single use. Also it is preferably transparent to enable light from a light source constituting part of the handle to illuminate the bowel wall and inner anus, so as to provide good visibility for the surgeon. Brief description of the drawings 10 By way of example, an embodiment of the above-described invention is described in more detail hereinafter with reference to the accompanying drawings. Figure 1 is a side elevation of an anal speculum according to the invention in combination with a handle and 15 introducer. Figure 2 is a view similar to figure 1 of the combination of that figure with the tubular probe and introducer shown in longitudinal-section. Figure 3 is a side elevation of the speculum appearing in 20 of Figure 1 drawn to an enlarged scale. Figure 4 is a longitudinal-sectional view of the speculum of figure 3. Figure 5 is a front end elevation of the speculum of Figure 3. 3 WO 01/43626 PCT/AU00/01526 Figure 6 is a rear end elevation of the speculum of figure 3. Figure 7 is a plan view of the speculum of figure 3 Figure 8 is a longitudinal-sectional view of the 5 introducer appearing in figure 1. Figure 9 is a side elevation of the introducer of figure 8 Best mode of carrying out the invention The combination illustrated by figures 1 and 2 comprises 10 a speculum 10 according to the invention, an introducer 11 and a handle 12. The speculum 10 is a one-piece moulding of a rigid transparent plastics material. It comprises a tubular body 13 having a leading end 14, a trailing, flared skirt 15 and an optical conductor 16 extending as a 15 cantilever from the skirt 15. In accordance with the invention the leading end 14 has a leading end face characterised by three, in this instance slightly tapering, elongate bights 17 equiangularly spaced apart by tongues 18 of arcuate cross-section. 20 As indicated earlier those bights 17 are adapted to pick up haemorrhoids which are guided by the side edges of the tongues 18 into the narrower, trailing ends of the bights where they may be readily accessed by a surgeon through the 4 WO 01/43626 PCT/AUOO/01526 skirt 15 and the bore of the tubular body 13 using well known and conventional surgical implements and procedures. To facilitate insertion of the speculum 10 into and through the anus of a patient an introducer 11 may be used, 5 and the present invention includes such an introducer and its use in conjunction with the speculum. The introducer 11 comprises a tapered tube having a smoothly rounded leading end 19 pierced by a small vent hole 20 and an enlarged, open, trailing skirt 20 which (see figure 2), comes into abutment 10 with the inner surface of the leading end of the skirt 15. As may be seen from Figures 1 and 2 the introducer 11 is dimensioned so that it may extend neatly through the speculum 10 until its rounded leading end 19 protrudes from the leading end of the speculum. 15 Following lodgment of the introducer 11 within the speculum 10, insertion of the speculum through the anus may be effected by manual pressure on the protruding trailing end of the introducer 17. Once insertion has been accomplished the introducer 11 may be withdrawn from the inserted speculum 20 for disposal or sterilisation and re-use. The handle 12 is a conventional item readily available from surgical instrument supply houses. It is in the nature of an electric torch, having a cylindrical body adapted to house replaceable batteries and a switch (not shown) in a 5 WO 01/43626 PCT/AUOO/01526 circuit for the energisation of a small but high-powered light bulb. The bulb is disposed at the inner end of a cylindrical socket in an end of the handle into which the optical conductor 16 is a tight but manually separable fit. 5 Thus the conductor 16 may simply be thrust into the socket to enable the handle not only to function as such for manipulation of the speculum as a whole but also to provide illumination at the site of the haemorrhoids being treated. 10 6