Charles Grant Blairfindie Allen, Popular Science Monthly (1879)
“ In the first place, this feather, as an anatomist would tell us, is "a dermal modification"—in other words, an altered bit of the skin. Every part of a plant or animal undergoes changes, our modern teachers say, just in accordance with the external influences which affect it. But the skin of an animal is naturally exposed to many more such surrounding agencies than its internal organs. ”
