the procedures around speculum use have also changed. Construction Specula have been made of glass or metal. They were generally made of stainless steel and sterilized between uses, but particularly in the 21st century, many — especially those used in emergency departments and doctor's offices — are made of plastic, and are disposable, single-use items. Those used in surgical suites are still commonly made of stainless steel. Types Specula come in a variety of shapes based on their purpose, and a variety of sizes; in any case the cylinder or blade(s) of the instrument allow the operator a direct vision of the area of interest and the possibility to introduce instruments for further interventions such as a biopsy. Vaginal The best-known speculum is the bivalved vaginal speculum; the two blades are hinged and are "closed" when the speculum is inserted to facilitate its entry and "opened" in its final position where they can be arrested by a screw mechanism, so that the operator is freed from keeping the blades apart. A cylindrical-shaped speculum, introduced in 2001, the dilating vaginal speculum (also known as the Veda-scope) invented by Clemens van der Weegen, inflates the vagina with filtered air. (see diagram) The device has two main functions: a) to take a normal Pap smear with a cervical brush or a cytology brush; and b) as an internal colposcope so that the operator can pivot the Veda-scope to view any part of the vagina barrel and cervix facilitated by an internal light source that can illuminate the vaginal wall and cervix with multi-coloured light filters, which can detect pre-cancerous cells with the aid of acetic acid solution and iodine solution. It also has a facility to attach a digital camera for viewing and recording. A specialized form of vaginal speculum is the weighted speculum, which consists of a broad half tube which is bent at about a 90 degree angle, with the channel of the tube on the exterior side of the angle. One end of the tube has a roughly spherical metal weight surrounding the channel of the speculum. A weighted speculum is placed in the vagina during vaginal surgery with the patient in the lithotomy position. The weight holds the speculum in place and frees the surgeon's hands for other tasks. A vaginal speculum is also used in fertility treatments, particularly artificial insemination, and allows the vaginal cavity to be opened