The nerves of touch in the skin.
The nerves of touch are not placed on the surface of the skin. We have really two skins, an outer and an inner one. The nerves are in the inner skin, and are covered by the outer skin. This outer skin is very thin except on the sole of the foot and the palm of the hand; from its thinness it is called the scarf-skin. It is this which is raised when a blister is drawn; and perhaps you know that it does not hurt to prick this when we want to let the water out; but if the needle touches the inner skin, where the nerves are, you feel it very quickly.
Now, when you touch any thing, the nerves in the inner skin feel it through this scarf-skin. This is so thin and soft that the nerves can feel through it; and, at the same time, it is a good protection to them. If it were not for this, the nerves would be affected too much by the rubbing of things against them. They could not even bear the air. If you had no scarf-skin you would be in great distress all the time. You know how much pain you suffer if you rub off the skin, as it is called, any where. It is the scarf-skin only that is rubbed off, and this exposes to the air the fine ends of the nerves in the inner skin.
The ends of the nerves of touch are in rows on the tips of the fingers. It is these rows that make the curved lines that you can see so plainly.
How some animals feel.
Whiskers of the cat.
There are no animals that have such perfect instruments of touch as our fingers are. Animals that have hoofs, as the horse and the cow, can not feel much with their fore feet. They have their sense of touch mostly in their lips and tongues. The elephant has this sense chiefly in the finger-shaped thing at the end of his trunk. There is not much feeling in the paws of dogs, cats, etc. The whiskers of the cat are feelers. There are nerves at the root of each of those long hairs, so that when any thing touches the whiskers the cat’s mind knows it at once.
Feelers of insects.
Insects have feelers extending out from their heads. Sometimes they are very long, as you see in this insect, called the ichneumon fly. We see insects, as they are going about, touch things with these feelers as we do with our hands. Bees can work in the dark, in their hives, guided by their feelers; indeed, the bee will not work at all if his feelers are cut off: he does not seem to know what to do with himself. Insects sometimes appear to tell each other things by their feelers. In every hive of bees there is a queen. If she dies, those that know about it go around very quickly, telling the other bees by striking their feelers with their own; and those that are told tell others, and thus the sad event is soon known all over the hive.