| pigments | Any normal or abnormal colouring matter in plants, animals, or micro-organisms. (12 Dec 1998) |
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| bile pigments | Colouring matters of the bile. They are bilirubin, biliverdin (biliverdine), bilifuscin, biliprasin, choleprasin, bilihumin, and bilicyanin. (12 Dec 1998) |
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| visual pigments | The photopigments in the retinal cones and rods that absorb light and initiate the visual process. (05 Mar 2000) |
| respiratory pigments | The oxygen-carrying (coloured) substances in blood and tissues (haemoglobin, myoglobin, haemocyanin, etc.). (05 Mar 2000) |
| retinal pigments | <ophthalmology, physiology> Chemicals functioning in the visual cycle in retinal rod cells. Through excitation by visible light, a series of complex molecular changes occur that serve to trigger in the optical nerve endings an impulse transmitted to the brain, resulting in the perception of vision. (12 Dec 1998) |