Its tact and the desire of colleagues to avoid distressing it by displaying negative emotions generally makes others willing to follow its advice – a pattern that one reviewer described as "a pleasant Machiavellian streak." Despite its natural timidity and the distress that other beings' anger, fear and pain cause it, Prilicla uses its empathic ability in prolonged searches for survivors of space combat and accidents. Major O'Mara The Earth-human head of the hospital's Psychology department, his job is to ensure that the hospital's diverse species work together as harmoniously, efficiently and safely as circumstances allow, and particularly to save the staff from being driven insane by over-use of Educator tapes. Since he is a very acute observer of behavior and often uses sarcasm "to shrink heads, not swell them", he is sometimes called a "latter-day Torquemada". Charge Nurse Naydrad A member of the Kelgian species, Naydrad looks like a giant caterpillar. Since the involuntary movements of Kelgians' fur completely show their emotions, the species is incapable of both lying and tact. Naydrad is a specialist in rescuing victims of space accidents. Thornnastor A native of the high-gravity planet Traltha, Thornnastor (nicknamed "Thorny") has a body like a six-legged elephant, and its own keen senses are supplemented by a symbiont that provides acute vision over up to 360 degrees. Thornnastor is the Diagnostician in Charge of Pathology, and it carries ten Educator tapes. Its fascination with gossip, especially about the scandalous activities of a multi-sexed, methane-breathing, cryogenic species, is a running gag in the series. Critical appraisal The Sector General series defined the subgenre of multi-species medical stories, although L. Ron Hubbard's Ole Doc Methuselah stories and Murray Leinster's Med Service stories, neither of which were highly regarded, had explored some similar themes. Sector General was "the first explicitly pacifist space opera" series, while much of contemporary space opera from the USA was notably military. Mike Resnick described the series' characters as "the most memorable crew of aliens ever created". Michael Ashley commented that the setting of the television series Star Trek: Deep Space Nine is reminiscent of Sector General. The Babylon 5 television series was also set in space station with atmospheres for different species. It is highly likely that the short lived 1998-99 television series Mercy Point was influenced by Sector General. Many commentators attribute the series' popularity to the altruism of its doctors and the emphasis on