a fibrous scleroprotein that occurs in the outer layer of the skin and in horny tissues such as hair feathers nails and hooves是什么意思_a fibrous scleroprotein that occurs in the outer layer of the skin and in horny tissues such as hair feathers nails and hooves在線(xiàn)翻譯_英語(yǔ)_讀音_用法_例句