Note 6 — Chapter V · ULTRA-VIOLET LIGHT IN HEALTH AND DISEASE

The only creature that has porphyrin as part of its normal body-covering is a tropical bird called the touraco, parts of whose feathers are dyed a brilliant red by a porphyrin-copper compound known as turacin. This pigment is remarkable also because it seems to be the only normal occurrence of copper as a coloring compound in feathers or skin. Turacin is soluble in weak alkali, so that when it rains and the bird comes into contact with such alkaline solutes as frequently occur in nature, the turacin bleaches out! Although porphyrin is rare as a normal coloring in adult animals, it is the commonest pigment found in the shells of birds’ eggs. Almost all eggs, from the hen’s brown to the robin’s blue, contain it.