Physiology

Techniques in genetics have advanced in the Culture to the point where bodies can be freed from built-in limitations. Citizens of the Culture refer to a normal human as "human-basic" and the vast majority opt for significant enhancements; severed limbs grow back, sexual physiology can be voluntarily changed from male to female and back (though the process itself takes time), sexual stimulation and endurance are strongly heightened in both sexes (something that is often subject of envious debate among other species), pain can be switched off, toxins can be bypassed away from the digestive system, automatic functions such as breathing or heart rate can be switched to conscious control, and bones and muscles adapt quickly to changes in gravity without the need to exercise. The degree of enhancement found in Culture individuals varies to taste, with certain of the more exotic enhancements limited to Special Circumstances personnel (for example, weapons systems embedded in various parts of the body).

Most Culture individuals opt to have drug glands that allow for hormonal levels and other chemical secretions to be consciously monitored, released and controlled. These allow owners to secrete on command any of a wide selection of synthetic drugs, from the merely relaxing to the mind-altering: 'Snap' is described in Use of Weapons and The Player of Games as "The Culture's favourite breakfast drug". "Sharp Blue" is described as a utility drug, as opposed to a sensory enhancer or a sexual stimulant, that helps in problem solving. "Quicken", mentioned in Excession, speeds up the user's neural processes so that time seems to slow down, allowing them to think and have mental conversation (for example with artificial intelligences) in far less time than it appears to take to the outside observer. "Sperk", as described in Matter, is a mood- and energy-enhancing drug, while other such self-produced drugs include "Calm", "Gain", "Charge", "Recall", "Diffuse", "Somnabsolute", "Softnow", "Focal", "Edge", "Drill", "Gung", and "Crystal Fugue State". The glanded substances have no permanent side-effects and are non-habit-forming.