194

ORIGIN OF THE SONGS OF BIRDS.

a repetition of one and the same note, is retained during life, and is generally common to both male and female. This stage in the notes of birds, is called recording, and is the first attempt of the nestling to sing, it may be aptly compared to the first attempts of the child to talk. At first, we are not able to perceive the least rudiment of the future song, but as the bird grows older and stronger, we see what he is aiming at. When the nestling is once sure of his strain, he commonly raises his voice, and sings out boldly; but he hurries over those parts of which he is not perfect master, lowering his voice as if he could not yet satisfy himself, and did not wish to be heard. The young bird commonly continues to record for ten or eleven months, when he is able to execute every part of his song, which afterwards continues fixed, and is scarcely ever altered. When the bird is thus perfect in his lesson, he is said to sing his song round.

Emily. Every species, I believe, has its own peculiar song-does this difference of song depend on a specific difference in the structure of the vocal organs ?

Dr. B.-It would seem very rational to suppose, that the physical organs being different, the sounds they produce, would be so of course. Yet it has been said that the song of birds is no more innate, than language in man, but depends on the master under which they are bred so far at least as their organs will enable them to imitate the sounds they hear. In proof of this opinion, many experiments have been related, in which birds have been taken from the nest while quite young, and removed to those of a different species. The results were, that the birds thus removed, had the song of their foster parents, and not of their own species.

Emily. These experiments then are perfectly satisfactory, I should think, in proving the truth of the opinion, that their songs are learnt, and not innate.

Dr. B. So it would seem, but most unluckily four or five years ago, (these experiments were performed in the last century) an intermeddling naturalist took it into

ACCURACY OF BIRDS' EAR.

195

his head to institute a series of similar experiments, and lo! their results were just the reverse. How to reconcile them, is more than we know, so that for the present we must be content to have no opinion on the subject.

Emily.-Verily, I think we are like the metaphysical ass between two bundles of hay, starving to death for lack of a sufficient motive to prefer one to the other.

Dr. B.-How birds originally came by the notes which are now peculiar to each species, we do not know; nor do we know why every nation has its peculiar language and music. The power of singing belongs but to few species of birds and is mostly confined to the males. In their wild state they do not generally sing more than two weeks in the year.

Emily.-Now however agreeable all this singing may be to us who hear it, I cannot, for my life, comprehend what important purpose in the economy of birds themselves, is answered by it.

Dr. B.-It would puzzle a wiser head than mine to enlighten you on this point. It has been supposed that the motive of the male bird in singing, is to amuse and solace his partner, during the tedious process of incubation. But surely this motive cannot induce birds kept in cages to sing as they do, nine or ten months in the

year.

Emily.-How accurate to, is the ear of singing birds! They readily learn any song from one another, and learn many of our common tunes from the flute or flagelet. I saw two or three years ago, in Boston, several robins which an old man had taught to sing yankee doodle perfectly. The mocking bird will sing almost any short strain after hearing it once or twice, and I have known a parrot which is not a singing bird, sing part of a catch with accuracy. Instances of Canary and other birds learning our music, are very common.

Dr. B.-But the accuracy of a birds' ear appears still more remarkable in this fact-that they always sing in the same key; and it is owing to this that we never

196

NOTATION OF BIRD'S SONGS.

hear a bird unable to complete his strain, as we often are, by taking a pitch above or below the compass of the

voice.

Emily.-Have there been any attempts made to reduce their songs to our musical notation? It would be quite pleasant to have the songs of some birds written out, and play them on the piano.

Dr. B.-Such attempts have been frequently made, but in most instances an insurmountable difficulty is found in the minuteness of their intervals. The smallest interval in common use in music, you know is the semitone, and although much smaller intervals are used in harmony, they are not easily appreciated in simple melody-probably on account of our being so accustomed to the grosser intervals. In some instances however, we find no difficulty in writing the notes of birds on our staff. The song of the cuckoo, is a well known and striking instance of this, in which the interval of minor third occurs. But our time is too far gone, to say any more on this subject.

THE BONES

197

CONVERSATION VIII.

Locomotive organs-bones-composition of bone-ossification-nutrition and reparation of bones-joints— skeleton-skeleton of the lower animals-adaptation of the human skeleton to the erect position-human foot and hand. The muscles-attachment of the muscles to the bones-action of the muscles on the principle of the lever. Standing-mechanical contrivances in the leg of birds-walking-teaping-running-influence of education on the muscles--gymnastic exercises.

Dr. B.-Having finished the functions of the nervous system, we come next to those of the locomotive organs; those by which we are enabled to act upon foreign objects, and transport our bodies from place to place according to the suggestions of the will. The organs of motion may be divided into classes; the active, and the passive-the former composing the muscles; the latter, the bones. And first let us speak of the bones.

Many of the inferior animals have in the interior of their bodies and limbs, a certain series of bones connected together by a definite method of arrangement, which so far as it exists, is generally the same in all. This series of bones is called the skeleton. It constitutes the basis and support of the soft parts, and gives to the body its general forms and dimensions. The substance of which a bone is composed, is of two kinds. That composing the external portion of the bone, is of a hard com

198

USE OF THE MARROW.

pact texture; while the centre is occupied by a substance of more soft and spongy nature. The proportions of these two parts vary in different bones, and in different portions of the same bone. Thus, the compact substance composes chiefly the shaft or body of the bone; while the head and the other extremity of the bone is formed almost wholly of the spongy substance surrounded by a thin covering of the compact. In the centre of the long bones, a hollow space is left which is filled by a fatty substance, called the marrow.

Emily.-I connot comprehend what purpose is answered by this spongy structure, which composes so great a portion of the bone. To me it seems to increase unnecessarily the size and weight of the bones, without adding in the least to their strength.

Dr. B.-You are entirely mistaken,-for the very effect of this kind of structure is to increase the strength of the bone. If the compact parts of the bone were all united together into a solid piece without any space in the centre, the bones being diminished in size, would more easily yield to external force; for it is demonstrated by mathematics, that the same quantity of matter in the form of a hollow cylinder is capable of resisting a greater external force, than in the form of a solid cylinder, the length being the same in both. Hence, it is generally found that in those parts of the body where strength is required without much additional weight, the bones have considerable spongy substance in their centre. Emily. And the marrow-what is the use of this? A store of nourishment laid up for the use of the bone?

Dr. B.-It cannot be for the nourishment of the bone, and yet it is difficult to say what its actual use is. It has been supposed to be diffused through the substance of the bone, and thus to render them less brittle. It has also been conjectured that its use in the animal economy is the same as that of other animal oils, and that the centre of the bones being a very convenient reservoir, it was placed here for this reason simply.