Gallifreyan physiology

Gallifreyans, despite being visually indistinguishable from Humans, had a variety of biological differences that set them apart.


 * Most of the known information of the Gallifreyans is based on the Time Lords, particularly the Doctor. Consequently, the following articles may have some inaccuracies due to these biases.

External appearance
Externally, Gallifreyans are identical to Humans, though they tend to have a mostly Eurasian appearance. Hair and eye colour may be of any colour found among Humans. (TDA: The Last Dodo)

Resilience
Gallifreyans are, on the whole, extremely tough and resilient. An average Gallifreyan is superior to the maximum skill of a Human. (DWN: Doctor Who and the Terror of the Autons)

Gallifreyans can survive extreme cold (DW: The Seeds of Doom, 42) and extreme heat (DW: The End of the World). They can even survive the subzero temperatures and extremely low pressure of vacuum for around 6 minutes (DW: Four to Doomsday), as well as electric shocks that would be fatal to Humans (DW: World War Three, Evolution of the Daleks). Röntgen radiation affects Gallifreyans so minimally that Gallifreyan children are routinely given radioactive toys in the nursery. They can, at will, absorb very high doses of Röntgen radiation, transform it into a form harmless to Humans, and expel it from their bodies. (DW: Smith and Jones) Radiation of other kinds can be fatal, but even then a Gallifreyan can hold out for a while after receiving these lethal doses. (DW: Planet of the Spiders)

Gallifreyans need less sleep than Humans do, and can make do with as little as an hour. (DW: The Talons of Weng-Chiang, DWN: The Highlanders)

A severely-injured Gallifreyan will generally slip into a healing coma, and devote all his or her energy to healing the injury. While in the coma, they may appear to be dead. (DW: Inferno, The Doctor's Daughter)

Even without regeneration, Gallifreyans had considerable lifespans. Within one regeneration, Gallifreyans could live for hundreds of years, yet looking much younger than a Human of equivalent age. (DW: The Leisure Hive)

Senses
Gallifreyans had all the senses of Humans, though theirs are generally superior to those of Humans. Gallifreyans also had extraordinary reflexes and precision timing, literally super-Human. (DWN: Doctor Who and the Terror of the Autons, DW: The End of the World, The Doctor's Daughter)


 * Sight: Gallifreyan eyes were better at seeing in the dark and could gather and enhance available light. (NA: Lucifer Rising)
 * Hearing: Gallifreyans had acute hearing. (REF: Doctor Who: The Visual Dictionary)
 * Taste: Using taste, the Doctor was able to identify the blood type of a sample. (DW: The Christmas Invasion, NA: Bad Therapy)
 * Smell: Gallifreyan's sense of smell was equal to their sense of taste. (TDA: Wishing Well)

As well as the senses shared with Humans, Gallifreyans have further senses, with at least an undefined Sixth Sense. (TDA: Wishing Well)

Body temperature
Gallifreyans had an internal body temperature of about 60 degrees Fahrenheit (16 degrees Celsius). (DW: Spearhead from Space, REF: Doctor Who: The Visual Dictionary)


 * Oddly, no Humans pointed out the differences in temperatures by touch. This might mean that this is a core temperature, whereas their skin temperature is closer to those of a Human.

The Brain
The Time Lord brain was much more complex than that of a Human brain and also larger. This size differences meant brain transplants into a Human body would be impossible. (DW: The Brain of Morbius) They were telepathically linked to one another and were even capable of joining the entire Time Lord intelligence as one. (DW: The Invisible Enemy) The Timewyrm noticed that on a quantum level, the Doctor's brain could receive information from possible futures, possibly without even realizing it consciously. (NA: Timewyrm: Revelation) Time Lords could also separate the hemispheres of their brain, allowing them to multi task easily. (PDA: Island of Death)

Time Lords had an additional lobe to their brain dedicated to mechanical and other bodily functions. (BFA: Spare Parts)

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. (NA: Blood Heat)

Circulatory system
Gallifreyan blood was different in composition from Human blood, as well as darker in colour and with a slight orange tinge to it. (DW: The Two Doctors, NA: The Left-Handed Hummingbird) The differences were readily apparent under a microscope. (DW: Spearhead from Space, The Invisible Enemy, Doctor Who: The TV Movie) It was highly adaptive, with regenerative properties. (TDA: The Art of Destruction) It didn't have the same A and B types as Human blood (i.e., the A and B antibodies are not present), and the extra-cellular matrix was incompatible with Earth-based life. (TDA: The Art of Destruction, DW: ''The Invisible Enemy')

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

Oldbood Gallifreyans Loomed after the Pythia's curse of sterility emerged with a single heart and gained their second only after their first regeneration. (MA: The Man in the Velvet Mask) Those of Newblood houses sprang from the Looms with two hearts from the outset. (NA: 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. (MA: Managra, EDA: The Adventuress of Henrietta Street, DW:The Shakespeare Code) Even if all the blood were removed from one cardiovascular system, the Gallifreyan could still survive. (DW: Smith and Jones) A Gallifreyan in total cardiac arrest will need CPR on both hearts. (DW: Smith and Jones)

Gallifreyans could, with training, stop their hearts and feign death, (DW: Destiny of the Daleks) and could slow them down significantly (TDA: Wishing Well). A dual cardiovascular system being more efficient, Gallifreyans typically had a resting pulse of only about 10 beats per minute. (DW: Spearhead from Space)

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. (PDA: Island of Death) They could also survive longer without much oxygen, past the point where a Human would be unconscious. (DW: The Ark in Space, Smith and Jones) Despite this, Gallifreyans (especially frailer individuals) could be affected by altitude sickness. (DWN: Marco Polo)

Like most aspects of Gallifreyan physiology, the respiratory system was largely under conscious control. Gallifreyans can, at will, enter a trance state which reduces the need for oxygen. (DW: Terror of the Zygons, Four to Doomsday) Gallifreyans also had a respiratory bypass system, which allowed them to survive strangulation. (DW: Pyramids of Mars, NA:Human Nature (novel))

Gallifreyans were immune to the effect of helium gas, which could make Human voices sound high-pitched and squeaky. (DW: The Robots of Death)

Biochemistry
Gallifreyans were similar to Humans in terms of biochemistry. This meant they could eat anything a Human could and could breath in the atmosphere of Earth. (NA: The Left-Handed Hummingbird) Despite this, the Gallifreyans had a number of differences.

Gallifreyans had a great degree of skill in controlling their own biochemistry. For example, they could counteract the negative properties of Psilocybin, modifying the chemicals into something harmless. Despite this, overdoses of drugs could still have an affect. (NA: The Left-Handed Hummingbird) Likewise, they were susceptible to the intoxicating effects of alcohol, but they could easily shrug off the effects when they needed to. (PDA: The Quantum Archangel, DW: The Girl in the Fireplace) As with Humans, however, excessive consumption could produce a hangover. (BBCR: Slipback)

Some Human medicines seem to work on Gallifreyans as well as Humans: some sleep-inducing drugs or toxic gases, for example. (DW: The Brain of Morbius) Anaesthetic gases of the type commonly administered before surgery, however, do not work well on Gallifreyans; a much greater quantity of anaesthetic must be administered, and even then it may not work completely. (DW:Doctor Who: The TV Movie) Finally, some Human medicines are catastrophically toxic to Gallifreyans: a single tablet of aspirin is enough to kill an adult Gallifreyan. (DW:The Mind of Evil)

Gallifreyans were as susceptible to Humans to the devastating effect of spectrox poisoning; spectrox toxaemia proceeds at roughly the same rate in both species, though a Gallifreyan, being tougher, will not succumb as quickly. (DW:The Caves of Androzani) They could counteract cyanide poisoning, given a number of ingredients (ginger beer, salt (from anchovies, as pure salt is "too salty"), walnuts) and a physical or mental shock, but only if done very soon after the cyanide is ingested. (DW:The Unicorn and the Wasp)