closed eyes. On the other hand, the risk of finding members of other species sexually attractive is a serious concern. Junior doctors usually have these acquired memories erased as soon as possible. However, as a doctor rises up through the hospital hierarchy, and if its mind proves to be sufficiently stable, it may find itself the permanent recipient of one or more tapes. Diagnosticians, the medical elite of Sector General, can have as many as ten different tapes active at one time, as they may have to supervise treatment of many species at the same time. In the case of species with two permanent sexes, including but not limited to Earth-humans, the stories state that females are psychologically incapable of allowing their psyches to be violated to the extent required by the educator tapes. However, in one of the later books a very assertive non-human female character accidentally acquires several sets of memories which cannot be erased, and adjusts to this with relative ease. Regular characters Although many of the characters are "Earth-human" – "human" is ambiguous because all species refers to themselves as "human" in their own languages – the stories feature medical staff from a wide range of species. In each story characters belonging to species different from that of the protagonist are treated as neuter and referred to as "it". Some species are touchy about any reference to sexual roles and behavior, some have more than two sexes and some change sex once or more during their lifetimes. The following appear in nearly all the stories: Dr. Conway A male Earth-human who starts as a junior intern and, over the course of the series, works his way up to Chief Surgeon and eventually Diagnostician in Charge of Surgery. Conway (whose first name, Peter, is only revealed in the ninth book) generally prefers extraterrestrial company to that of his own species, and has a habit of thinking aloud. His passions are healing and Murchison. Murchison A curvaceous female Earth-human first seen as a senior nurse in the Pathology department. She eventually becomes a doctor and a Pathologist herself, and also Conway's wife. Dr. Prilicla A large but fragile winged insect-like being from the very low-gravity planet Cinruss. In addition to being highly skilled in the more delicate types of surgery, Prilicla is an empath and therefore can sense the emotions of most other lifeforms including many non-intelligent animals.