Feathers are modifications of the scarf-skin. Wherever the skin is exposed to sun, wind, or water it is modified in some way to contribute to the well-being of the animal. The many forms of feathers make a most fascinating study.
A peculiar thing about them is that they are not vascular. Vascular means full of vessels. Almost everything that grows is vascular. It has tubes to carry in new material and little sacs or large ones to store substance for new growths. But dermal appendages, the forms that grow out of the scarf-skin and are modifications of it, are not vascular. Take a feather two feet long, and examine it to see how the feather material was carried from the beginning of the quill to the tip. You find no veins and no circulation. Yet feathers grow and their growth is quite mysterious and not understood by the wisest people.
The material of a feather consists of cells that push each other out to their destination. They change their forms as they travel along, and their colors and degrees of hardness change with their going. They are composed of about the same stuff that makes horns and hoofs. Your finger nail is like a feather in its growth and composition. It is mostly albumen with some lime in it. Albumen is the substance which makes the white of eggs.
When the Mexican motmot trims his two tail feathers with his beak, he merely makes diamond cut diamond. The material of the cutting instrument is the same as that of the thing cut, only somewhat harder.
When you consider how a feather grows by pushing out its cells you must wonder at the intelligence which guides the cells to change their nature so as to form the quill, the shaft, the after-shaft, the barb, the barbules, and the little hooks which hold them together. More than this is the cause for admiration seen in the regular change of pigment contained in the cells, so the feather shall have its beautiful colors and accurate markings.
Along with the materials of the feather is carried a little oil which turns the water from the duck's back and gives the feather its gloss. It is thought by some that the fading of feathers in museums where mounted specimens are exposed to the action of light is largely due to the loss of this delicate oil. No enterprising Yankee has come forward yet with a patent for restoring this oil and giving back to the thousands of musty and dusty skins in our museums their original brilliancy.
Every one wonders at the way feathers keep their shape instead of getting hopelessly ruffled. The little hooks which hold the barbules together are exceedingly strong and flexible. They will yield and bend, but never break. Even when torn apart from their hold they can grasp again so as to restore the injured feather to its former shape.
VISION AND SCENT OF VULTURES.
REV. R. T. NICHOL.