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"The antitragus (d) is the small eminence situated a little below the posterior extremity of the antihelix, and opposite

to the tragus.

"The cavitas innominata (e) is the curved depression which is situated between the helix and antihelix.

"The scapha, or fossa navicularis (ƒ), is the small depression between the divisions of the anterior extremity of the antihelix.

"The concha (g) is the large cavity which is bounded above by the antihelix, below by the lobus, before by the tragus, and behind by the antitragus. It is divided by the anterior extremity of the helix into a small superior and a large inferior chamber, of which the latter leads to the meatus auditorius externus.

"The lobus is situated at the inferior part of the ala. It is composed of a cellular substance, with a small quantity of fat, and forms the inferior soft part of the auricle.

"On the posterior surface of the auricle we observe a considerable eminence, called the dorsum of the concha."

For this anatomical description we are indebted to Mr. Tod, from whose work also the following account is in part collected. Connected with the concha there is a narrow tube, formed of bone and cartilage, called the meatus auditorius externus, A B of the accompanying figure. It is an oval canal, about three quarters of an inch in length, but differs considerably in diameter at different parts; it is smallest in the middle, and larger at the external than the internal extremity. "It leads," says the author already quoted, "obliquely forwards and inwards, from the inferior chamber of the concha; and in its course proceeds a little upwards, then downwards at its

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internal extremity, and terminates upon the surface of the membrana tympani, F. These curves, however, are very inconsiderable, for the internal extremity of the canal can be easily seen in a clear light, when the auricle is drawn a little backwards. This tube is defended from the injury that might arise from the access of dust and small insects, by fine hairs, and a viscous secretion called cerumen, or wax, produced by a number of small glands, known as the glandulæ ceruminosæ. Another effect resulting from this secretion is the dif

fusion of a moisture over the tympanum, thereby softening down the sonorous impulses, and rendering the membrane itself more sensible."

The eustachian tube, H G I, is connected with this cavity, and opens into the mouth. Behind the tympanum is a complicated apparatus, B C P, which is shown in detail in figure 4.

The tympanum, F, or drum of the ear, is composed of two nearly circular membranes. In children it is of an oval form. This membrane separates the external and internal ear, and "forms a completely impervous septum ; and from its extremely delicate and sensible texture, tension, concave and convex obliquity, is rendered capable of being stimulated by a very small impulse of sound; and of being moved, by the muscles of the cavitas tympani, with the utmost facility. It also prevents all extraneous matter, as well as sonorous pulses transmitted by the air, from irritating the cavitas tympani."

Having presented to the reader a condensed anatomical description of the external ear in man, many curious and interesting inquiries immediately suggest themselves to our mind. All animals do not possess an external ear, and the form varies considerably in the several species who are provided with this appendage. The external ear and tympanum is confined to vertebrated animals, and all these do not possess them. Reptiles, fishes, worms, and insects, have neither auricle or meatus; and in birds the auricle is in the least possibly perfect state. Among this class of animals, however, there is a considerable variety in the degree of development. The carnivorous class have it much larger than the grami

THE FORM OF THE EXTERNAL EAR.

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nivorous; and the birds which seek their prey by night, larger than those which procure it in the day. The lastmentioned fact certainly appears rather singular; for, as it has been already remarked, the sounds are transmitted with greater facility during the night than the day. This may not, however, be sufficient to recompense the animal for the want of light, and a more perfect organ of hearing may consequently have been provided.

The form and position of the external ear, and its capability of motion, vary considerably in different quadrupeds. The ears of rabbits and hares are large, and have a great readiness of motion. They are also so placed as to enable them to hear sounds which are produced behind them. The reason of this is evident; the animals are exposed to many dangers, and have no means of defence. Their chance of safety depends upon the swiftness of feet and the readiness of hearing. Rapacious animals, such as the lion, tiger, and cat, have their ears directed forward, and are not nearly so large in proportion to their bulk or strength as in the hare. The elephant also, a large animal of great physical power and capable of self-defence, has a comparatively small ear. It would appear, then, that the Creator has given such forms and sizes to the ears of animals as are best suited to their habits and characters. To those which have been denied weapons of defence, and are by nature timid, He has given such an acuteness of the senses, as enables them to avoid their enemies by flight or by cunning.

Some writers have maintained, that the external ear of animals is intended as an ornament, and not as a useful or necessary part of the organ of hearing. This opinion has

been supported by the statement that the hearing of the horse or dog is not injured by cropping. No proof, however, can be given of this. That the sense of hearing continues after a portion of the external ear has been removed there is no doubt, but that it is unimpaired we have no evidence. The remarks which have already been made on the external ear will be sufficient to prove, that this opinion is not founded in fact; and although the human ear is incapable of motion like that of other animals, yet it is provided with muscles which, acting upon its several parts, dilate and contract the opening of the meatus, and have some action on the tympanum. That the auricle is of secondary importance in hearing is evident from a variety of circumstances, and not least from its exposure; for we find that in all cases the delicate portions of an organ most important as a medium in producing sensation, are protected. Still it has a purpose in the collection of sounds even in man, who is not able to give it motion. Were it not for the power which some animals have of giving motion to the external ear, "many of the inferior animals would be left without some of their most valuable endowments. The dog, for example, when he loses the scent, but not the sound of his master, would never be able to find him out without this admirable provision. When so situated, we observe that he immediately raises his head, shuts his mouth, erects his auriculæ, and has their concave surfaces directed generally forwards. Then he may be considered as listening with the greatest attention, and in the very best position for that purpose; for by raising his head he becomes enabled to receive the anticipated effect with great facility; by shutting his mouth the anterior auris muscle of each auricle

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