individual, consisting of a semi-circular portion, spread out, the shape of which everybody knows, and a passage in the middle, leading into the head.

The external ear, which we see, is made of gristle or cartilage, covered with the skin. It is concave, for the collection of sound. Such is the curious structure of the eye, that the rays of light, from all directions, are collected into a very small point at the back part of it; and in like manner, such is the structure of the external ear, that sound is collected by it towards the passage, in the

centre.

This passage is lined by a membrane like the skin, except that it is a little thinner, the oil glands more numerous, and the oil very bitter. What is called the ear-wax is this oil, dried, and accumulated in large quantities. Sometimes it has been known to accumulate in such hard masses, and of such a size, as to make people deaf, by obstructing the passage of sound. There was lately a case of the kind in this neighborhood. Both ears were thus obstructed, but one was much worse off than the other.

This oil or wax is supposed to have been made bitter, to keep flies and other insects from getting into the ear; for these insects dislike bitter substances. There is, however, less danger from having insects get into the ear than is commonly supposed; for when the ear drum, or membrane of the tympanum, of which I have spoken in another place, is not ruptured, neither insects nor anything else can get into the head more than three quarters of an inch, and could easily be washed out. Still, they might produce some irritation, and they are therefore excluded by the means spoken of.

If, however, the ears are washed out well every day, and especially if they are often syringed out with weak soap suds and water, we shall seldom have trouble, either from the collection of wax or from insects. Cleanliness is very important, not only in the case of the ear, but of all parts of the body.

Beyond the drum is a chamber, called by anatomists the cavity of the tympanum. In this cavity are the little bones which I have formerly described. Here also a small passage commences, which terminates near the back

part of the nostrils, called the eustachian tube. The use of this passage, from the inside of the mouth to the internal ear, is not very well known; but it is believed to be intended, in part, for the purpose of letting in air, in order that the pressure on both sides of the drum may be alike.

Some suppose that it enables us to hear a little through the mouth; but this is not probable. If we hear at all through the mouth, it is in a degree scarcely worth mentioning.

Near the hinder part of this cavity of the tympanum, there is also an opening into a collection of cells in the bone. The part of the head in which these cells are situated may be found quite prominent behind the ear. The use of the cells is not very well known.

Though the ear is to be considered a door of the human habitation, the passage into it, as we have seen, is usually closed by the ear drum. The door-way for everything except sound, therefore, would be more properly through the mouth.

Sometimes we know not how the drum membrane gets broken. There have been

men, for example, who could force tobacco smoke, held in their mouth, out at their ears. This proves that the membrane in question had a hole in it. I do not know that such a breach affects the hearing very much. It is true it requires us to be more cautious what we get into our ears; for if substances go beyond the ear drum quite into the cavity of the tympanum, they will produce inflammation; and in the end, perhaps, cause deafness or death.

I wish I had room to tell you more about this cavity of the ear, and indeed about the whole organ of hearing; for it is a very curious organ.

But all I can say, which will probably be useful to you at present, is a few words about the labyrinth. This is a large cavity, still deeper in the head than the foregoing; and, if possible, still more curious in its structure.

The middle part of the cavity is called the vestibule. It is somewhat oval in shape. At one end of it are three tubes, each of which is so bent or curved as to form almost a circle. They open into the vestibule, and are called semi-circular canals.

At the other end of the vestibule is a tube of a conical shape, but resembling, on its outside, the shell of a snail. It is called the cochlea. This also opens into the vestibule.

The little bones of the ear are connected with the ear drum on one side, and with the parts of the labyrinth just described on the other. The labyrinth, in all its parts, is most intimately connected with the brain; and some