Gallifreyan physiology

Gallifreyans were outwardly indistinguishable from humans. They had a variety of biological differences that set them apart.

Most of the known information on Gallifreyans is based on Time Lords, particularly the Doctor. It has been unclear for some time if the terms "Gallifreyan" and "Time Lord" are interchangeable, or if "Time Lord/Lady" is a specific rank within the society, possibly with some specialised abilities. Consequently, the following articles may have some inaccuracies due to these assumptions.

It is believed many traits of the Time Lords developed over time due to exposure to the Time Vortex. This was possible for humans as well as Gallifreyans. River Song also developed some of these traits, despite both her parents being human, because she had been conceived within the Vortex itself. (TV: A Good Man Goes to War)

Taxonomy

The Gallifreyans were classified by humans as Dominus temporis. (PROSE: The Last Dodo) Despite appearances, the Gallifreyans were more closely related to Terileptils than humans. (TV: The Visitation) The Eleventh Doctor also once stated that he was "not an ape" (TV: Cold Blood) and the Tenth Doctor stated that they did not evolve from apes. (TV: The Doctor's Daughter)

He may also simply have meant that he was not human, as the Silurians to which he was speaking referred to humans as "apes".

External appearance

Externally, Gallifreyans were usually identical to humans, though they tended to have a mostly Eurasian appearance. Hair and eye colour were of any colour found among humans. (PROSE: The Last Dodo) Teeth were indistinguishable from human teeth. (TV: The Gunfighters, Utopia) However, while Romana I was regenerating into Romana II, she took on various appearances varying in height and build, and even one with blue skin. (TV: Destiny of the Daleks) The Ninth Doctor referred to the regeneration process as "dodgy," and indicated that it was possible to regenerate without a head. (TV: The Parting of Ways)

The Doctor, especially his Seventh incarnation, appeared to have uncertain eye colours. Whether this was an actual ability of the Gallifreyans to change their eye colours or simply due to others' perception is unknown. (PROSE: Blood Heat, Legacy)

Resilience

Gallifreyans were, on the whole, extremely tough and resilient. An average Gallifreyan was superior to a human at their peak. (PROSE: Doctor Who and the Terror of the Autons)

Gallifreyans could survive falls (and probably many other physical stresses) which would shatter the bones of humans. (TV: The End of Time) Gallifreyans could survive extreme cold (TV: The Tomb of the Cybermen, The Seeds of Doom, The Ribos Operation, 42, The Infinite Quest, Planet of the Ood), due to having a "souped-up metabolism" (COMIC: The Betrothal of Sontar). They could also survive extreme heat. (TV: The End of the World) They could even survive the subzero temperatures and extremely low pressure of vacuum for around six minutes (TV: Four to Doomsday, The Doctor, The Widow and the Wardrobe), as well as electric shocks that would be fatal to humans (TV: Genesis of the Daleks, Terror of the Zygons, World War Three, Evolution of the Daleks, The Vampires of Venice, The Pandorica Opens). Röntgen radiation affected Gallifreyans so minimally that Gallifreyan children were routinely given radioactive toys in the nursery. They could, at will, absorb very high doses of Röntgen radiation, transform it into a form harmless to humans, and expel it from their bodies. (TV: Smith and Jones) Radiation of other kinds could be fatal, but even then a Gallifreyan could hold out for a while after receiving these lethal doses. (TV: Planet of the Spiders, The End of Time)

Gallifreyans needed less sleep than humans, and could make do with as little as an hour. (TV: The Talons of Weng-Chiang, PROSE: The Highlanders)

A severely-injured Gallifreyan would generally slip into a healing coma, and devote all his or her energy to healing the injury. While in the coma, they would appear to be dead. (TV: Inferno, Planet of the Daleks)

Time Lords also seem to have an increased resilience to higher frequencies of sound (TV: The Christmas Invasion, Partners in Crime)

Gallifreyans could be disabled by a blow to the left shoulder, which possessed a vulnerable nerve cluster. (PROSE: Set Piece)

Lifespan

Even without regeneration, Gallifreyans had considerable lifespans. Within one regeneration, Gallifreyans could live for hundreds of years, yet look much younger than a human of equivalent age. When artificially aged 500 years, the Fourth Doctor looked like an elderly human (TV: The Leisure Hive), whereas his eleventh incarnation looked the same for two centuries (TV: The Impossible Astronaut).

However, Gallifreyan children and teenagers grew at about the same rate as humans of the same age. (TV: An Unearthly Child, The Sound of Drums) After this point, ageing would slow, with the Gallifreyan looking like a teenager for decades. (PROSE: Legacy of the Daleks) Ninety years was still considered childhood. (TV: The Stolen Earth)

The maximum lifespan of Time Lords was unknown. The Second Doctor once stated, that barring accidents, they could live forever. (TV: The War Games) They considered 750 middle-age. (TV: Pyramids of Mars) One Time Lord, Quences, died when he was over 7,000 years old. (PROSE: Lungbarrow) Professor Chronotis suffered from senility when over 12,000 years old. (PROSE: Shada)

Senses

Gallifreyans had all the senses possessed by humans, and to generally superior degrees. Gallifreyans also had extraordinary reflexes and precision timing, literally superhuman. (PROSE: Doctor Who and the Terror of the Autons, TV: The End of the World, The Doctor's Daughter) The Third Doctor stated that their reflexes were ten times a human's. (TV: The Time Monster) Gallifreyans showed great hand-eye coordination and dexterity with a wide variety of tool and weapons. (TV: The Android Invasion, Human Nature, The Pirate Planet) Gallifreyans (in 'younger' bodies) were, consequently, very physically able. The Third Doctor was a martial arts master, the Fifth Doctor (much like, latently, the Tenth) was a skilled cricketer , and the Eleventh Doctor discovered a natural talent for football. (TV: The Lodger)

• Sight: Gallifreyan eyes were better at seeing in the dark and could gather and enhance available light. (PROSE: Lucifer Rising) They could notice small objects or details from distances of at least twenty feet away (TV: The Eleventh Hour) as well as people that were quite a distance away. (TV: The Hungry Earth)
• Hearing: The Tenth Doctor exhibited Gallifreyan hearing by perceiving sounds from the TARDIS, while located several sections away, aboard the airship Valiant. (TV: The Sound of Drums)
• Taste: Using taste, the Seventh and Tenth Doctor were able to identify the blood type of a sample. (TV: The Christmas Invasion, PROSE: Bad Therapy) The Tenth was also able to identify types of wood (TV: Tooth and Claw) and of metal. (TV: The Idiot's Lantern) The Eleventh Doctor was able to tell how much a shed had aged via taste. (TV: The Eleventh Hour) The Eleventh Doctor could determine the chemical and mineral composition of blue grass by tasting it. (TV: The Hungry Earth) The Eleventh Doctor could tell where the four TARDIS blue envelopes were made by taste. (TV: Day of the Moon)
• Smell: The Gallifreyan sense of smell was equal to their sense of taste. (PROSE: Wishing Well) They could do a chemical analysis of the air using their sense of smell. (PROSE: Doctor Who and the Carnival of Monsters) On some occasions Time Lords were also able to judge what time period and location they were in by the smell of the air. (TV: The Unicorn and the Wasp) Gallifreyans were capable of locating one another over great distances through "smell". (TV: The End of Time)
• Proprioception: Gallifreyans were better at coping with sudden changes in position than humans and were harder to disorient. (AUDIO: The Forever Trap)

As well as the senses shared with humans, Gallifreyans had further senses, with at least an undefined Sixth Sense. (PROSE: Wishing Well) Gallifreyans had time- and spatial-related senses and physical attributes; they were able to resist fields of slow time (TV: The Time Monster, Invasion of the Dinosaurs), notice distortions and jumps in time (TV: Invasion of the Dinosaurs, City of Death, The Lodger), directly perceive the interstellar motions of cosmological bodies or their inhabitants (TV: Rose), and perceive all possible timelines (TV: The Parting of the Ways, The Fires of Pompeii). Gallifreyans could sense the presence of others of their own species, with the sense being specific enough to allow identification of one another just by sight, regardless of potential recent regeneration. (TV: The Sound of Drums)

Internal anatomy

Body temperature

Gallifreyans had an internal body temperature of about sixty degrees Fahrenheit (sixteen degrees Celsius). (AUDIO: Blood of the Daleks, REF: Doctor Who: The Visual Dictionary) While recovering from a serious injury, it could drop spontaneously to below-freezing temperatures. (TV: Planet of the Daleks)

Oddly, no humans pointed out the differences in temperatures by touch. This might mean that this was a core temperature, while their skin temperature was closer to those of a human.

The Brain

The Time Lord brain was much larger and more complex than the human brain. The size differences effectively ruled out brain transplants from a Gallifreyan to a human. (TV: The Brain of Morbius) They had a form of photographic memory, able to recall every detail of even the most insignificant moments in time. (TV: The Eleventh Hour) The Timewyrm noticed that on a quantum level, the Seventh Doctor's brain could receive information from possible futures, possibly without even realising it consciously. (PROSE: Timewyrm: Revelation) Time Lords could also separate the hemispheres of their brain, allowing them to multitask easily. (PROSE: Island of Death) The autonomic functions could be artificially supplanted with a special device, allowing the Gallifreyan to think with their autonomic brain. (PROSE: Shada)

Time Lords had an additional brain lobe dedicated to mechanical and other bodily functions, freeing the other lobes for intellectual endeavours. (AUDIO: Spare Parts)

Time Lords displayed the ability of touch-enabled mental manipulation; this has manifested itself in a number of different ways, including hypnosis (TV: Terror of the Autons, The Ribos Operation), mind-reading (TV: The Girl in the Fireplace), thought sharing (TV: The End of Time), the ability to relieve dementia (at least externally caused dementia) (TV: The Shakespeare Code), mentally influencing the dreams of others (TV: The Eleventh Hour) and memory erasure (TV: Journey's End). They could also transfer knowledge quickly to another person by headbutting them. (TV: The Lodger)

Time Lords were telepathically linked to one another and could join the entire Time Lord intelligence as one. (TV: The Invisible Enemy) They could hold telepathic conversations over distances, but this was more difficult. (TV: The Sensorites, The Three Doctors, The Pirate Planet) They could converse with each over the astral plane, although this ability required intense concentration, and an interruption might have fatal consequences for the Time Lord. (TV: The Two Doctors) Their telepathy extended to less intelligent animals. (TV: The Lodger) In ancient times, Gallifreyans who were capable of blocking out the telepathic thoughts of other Gallifreyans were called Individuals. They usually had red-gold hair and often went on to become Young Heroes. (PROSE: Cat's Cradle: Time's Crucible)

Time Lords were vulnerable to powerful hypnosis, such as the Morpho or the Great Vampires employed. (TV: "The Velvet Web", State of Decay) They were more resistant against if not immune to other forms of mind control. (TV: The War Machines, The Green Death)

Skeletal structure

Gallifreyan skeletal structure was identical to human skeletal structure, with the exception of the rib cage: Gallifreyans had 26 ribs, two more than humans. (PROSE: Blood Heat)

Circulatory system

Gallifreyan blood was different from human blood, darker and with a slight orange tinge to it. (TV: The Two Doctors, PROSE: The Left-Handed Hummingbird) The differences were readily apparent under a microscope. (TV: Spearhead from Space, The Invisible Enemy, Doctor Who) It was highly adaptive, with regenerative properties. (PROSE: The Art of Destruction) It didn't have the same A and B types as human blood (i.e., the A and B antibodies were not present). The extra-cellular matrix was incompatible with Earth-based life and the structure of haemoglobin was different. (PROSE: The Art of Destruction, TV: The Invisible Enemy, PROSE: Placebo Effect)

Binary vascular system

Gallifreyans naturally born before the time of Rassilon and Pythia had two hearts. (PROSE: Cat's Cradle: Time's Crucible, Lungbarrow)

A scan taken by Kate Stewart reveals both the Doctor's hearts. (TV: The Power of Three)

Accounts differ as to the vascular systems of Gallifreyans in their first incarnation. Some accounts indicate that Gallifreyans normally had two hearts even in their first body. (AUDIO: Frostfire, TV: The Doctor's Daughter) Other accounts indicate that Oldblood Gallifreyans Loomed after the Pythia's curse of sterility emerged with a single heart and gained their second only after their first regeneration, (PROSE: The Man in the Velvet Mask) while those of Newblood houses sprang from the Looms with two hearts from the outset. (PROSE: Christmas on a Rational Planet)

A Gallifreyan could survive with only one heart, should the other be punctured or destroyed, though he or she would be weakened greatly. (PROSE: Managra, PROSE: The Adventuress of Henrietta Street, TV:The Shakespeare Code) Even if all the blood were removed from one cardiovascular system, a Gallifreyan could still survive. A Gallifreyan in total cardiac arrest would need CPR on both hearts. (TV: Smith and Jones) Regeneration would become impossible if both hearts were burnt out simultaneously. (TV: Forest of the Dead)

Gallifreyans could, with training, gain conscious control over their hearts, enabling them to stop their hearts and feign death, (TV: Destiny of the Daleks) and could slow them down significantly (TV: Terror of the Zygons, PROSE: Wishing Well). They could even control blood vessels, dilating and contracting them at will. (PROSE: Cat's Cradle: Witch Mark) A dual cardiovascular system being more efficient, Gallifreyans had a resting pulse of as few as ten beats per minute. (TV: Spearhead from Space) Under stress, the hearts' rates could seem dangerously fast and irregular to human doctors. (TV: Doctor Who) Two pulses could be detected in the wrist. (TV: The Five Doctors, Time and the Rani)

Respiratory system

In order to use their two hearts, Gallifryans had an advanced respiratory system. Instead of large lungs, they had a series of pulmonary tubes parallel to the lymphatic system. This made them positively buoyant, allowing them to swim with ease. (PROSE: Island of Death) They could survive longer without much oxygen, past the point where a human would be unconscious. (TV: The Ark in Space, The Two Doctors, Smith and Jones, PROSE: Legacy) Despite this, Gallifreyans (especially frailer individuals) could be affected by altitude sickness. (PROSE: Marco Polo)

Like most aspects of Gallifreyan physiology, the respiratory system was largely under conscious control. Gallifreyans could, at will, enter a trance state which reduced the need for oxygen. (TV: Terror of the Zygons, Four to Doomsday) Gallifreyans also had a respiratory bypass system, which allowed them to survive strangulation (TV: Pyramids of Mars, PROSE: Human Nature), avoid breathing poison gas (TV: The Two Doctors), and stave off drowning. (PROSE: Killing Ground)

Gallifreyans were immune to the effect of helium gas, which could make human voices sound high-pitched and squeaky (though this was implied to be a learned technique rather than an innate ability). (TV: The Robots of Death)

Other Organs

The skin of a Gallifreyan had more subdural and subcutaneous layers than a human, adding considerably to its durability and damage resistance. Gallifreyan skin tended to reject foreign objects such as subcutaneous implants or tags relatively quickly, (PROSE: Burning Heart) though such implants were deliberately retained on occasion, suggesting this to be another consciously controllable ability. (TV: Day of the Moon)

Gallifreyan physiology has been described by a human medic as having "four of everything he should have two of and two of everything else." (PROSE: Burning Heart) The Gallifreyans had two livers. (PROSE: Halflife) They also had several organs which had no analogue in humans. (PROSE: Placebo Effect)

Due to internal incompatibilities, Gallifreyans were not suitable for certain forms of Cyber-conversion. (TV: Closing Time)

Gallifreyans also had DNA in a triple-helix formation. (PROSE: The Crystal Bucephalus)

The Tenth Doctor, expelling cyanide from his system. (TV: The Unicorn and the Wasp)

Biochemistry

On the whole, Gallifreyan biochemistry seems to have been quite similar to human biochemistry: they could eat anything humans could and could breathe on Earth. (PROSE: The Left-Handed Hummingbird)

Gallifreyan biochemistry, like many other aspects of Gallifreyan physiology, was subject to the conscious control of the individual. For example, a Gallifreyan was able to counteract the negative properties of Psilocybin by modifying the chemicals into something harmless, though the techniques were not foolproof and drug overdoses were still possible. (PROSE: The Left-Handed Hummingbird) Similarly, though Gallifreyans were susceptible to the intoxicating effects of alcohol, they could easily shrug off the effects when they needed to. (PROSE: The Quantum Archangel, TV: The Girl in the Fireplace) As with humans, however, excessive consumption could produce a hangover. (AUDIO: Slipback) Ginger beer would reduce their ability to tolerate alcohol. (AUDIO: The Kingmaker)

Some human medicines seem to have worked on Gallifreyans as well as humans: some sleep-inducing drugs or toxic gases, for example. (TV: The Brain of Morbius) Anaesthetic gases of the type commonly administered before surgery, however, did not work well on Gallifreyans; a much greater quantity of anaesthetic could be administered, and even then it might not work completely. (TV: Doctor Who) Aspirin was toxic to Gallifreyans; a single dose could kill one. (TV: The Mind of Evil, PROSE: The Left-Handed Hummingbird) It was said to either fatally stop platelet aggregation (AUDIO: The Condemned), cause massive allergic, pulmonary and cerebral embolism (PROSE: Burning Heart), or interfere with the hormone receptor intermediaries (PROSE: The Taking of Planet 5). Death could be prevented by entering a deep coma which was outwardly mistakable for death (PROSE: Burning Heart), or by ingesting chocolate. (AUDIO: The Condemned)

Other sleep-inducing drugs might work on a Gallifreyan, but would take roughly twice as long as with humans, even if the Time Lord in question took double the dosage that the humans had. (TV: The Androids of Tara)

Gallifreyans were as susceptible as humans to the devastating effect of spectrox poisoning; spectrox toxaemia proceeded at roughly the same rate in both species, though a Gallifreyan, being tougher, would not succumb as quickly. (TV: The Caves of Androzani) They could counteract cyanide poisoning, given a number of ingredients including ginger beer, something salty (but not salt), protein and a physical or mental shock, but only if done very soon after the cyanide is ingested. (TV: The Unicorn and the Wasp)

Mustard gas would kill a Gallifreyan as much as a human. (AUDIO: The Great War)

During a decontamination attempt by Silurians intended for humans, the Eleventh Doctor claimed that removing the germs would remove half of the things keeping him alive, suggesting further differences. (TV: Cold Blood)