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Show 20 THE DESCENT OF 1\IAN. PART I. currecl in the proportion of about 3 per cent. in upwards of GOO bodies : he adds, that this muscle affords " an " excellent illustration of the statement that occasional " and rudimentary structures are especially liable to " variation in arrangement." Some few persons have the power of contracting the superficial muscles on their scalps ; and these muscles are in a variable and partially rudimentary condition. 1\'I. A. • de Candolle has communicated to me a curious instance of the long-continued persistence or inheritance of this power, as well as of its unusual development. He knows a family, in which one member, the present head of a family, could, when a youth, pitch several heavy books from his head by the movement of the scalp alone; and he won wagers by performing this feat. His father, uncle, grandfather, and all his three children possess the same power to the same unusual degree. This family became divided eight generations ago into two branches; so that the head of the above-mentioned branch is cousin in the seventh degree to the head of the other branch. This distant cousin resides in another part of France, and on being asked whether be possessed the same faculty, immediately exhibited his power. This case offers a good illustration how persistently an absolutely useless faculty may be transmitted. The extrinsic muscles which serve to move the whole external ear, and the intrinsic muscles which move the different parts, all of which belong to the system of the panniculus, are in a rudimentary condition in man ; they are also variable in development, or at least in function. I have seen one man who could draw his ears forwards, and another wlto could draw them backwards; 23 23 Canestrini quotes Hyrl. (' Annuario della Eoc. dei Naturalisti,' Modena. 1867, p. 97) to the Eame effect. CHAP. I. RuDIMENTS. 21 and from what one of these persons told me, it is probable that most of us by often touchinO' our ears and thus direct~ng our attention towards them, could by repeated trials recover some power of movement. The faculty of erecting the ears and of directinO' them to <.lifferent points of the compass, is no doubt of the highest service to many animals, as they thus perceive the point of danger; but I have never heard of a man who possessed the least power of erecting his ears,the one moYement which might be of use to him. The whole external shell of the ear may be considered a rudiment, ~ogether '~ith .the various folds and promine~ ces. (hehx and ant1-~ehx, tragus and anti-tragus, &c.) whiCh m the lower ammals strengthen and support the ear when erect, without adding much to its weight. Some authors, however, suppose that the cartilage of the shell serves to transmit vibrations to the acoustic nerve ; b~t Mr. To):nbee, 24 after collecting all the lmown evidence on this head, coneludes that the exter-nal shell is of no distinct use. The ears of the chimpanzee and orang are curiously like those of man, and I am assured by the keepers in the Zoological Garden:.; that these animals never move or erect them; so that they ~re ~nan equally rudimentary condition, as far as functwn Is concerned, as in man. vVhy these animals, as well as the progenitors of man, should have lost the power of erecting their ears we cannot say. It may be, though I am not quite satisfied with this view that owinO' to th.eir arboreal habits and great strength they wer~ but. little exposed .to danger, and so during a lengthened peno~ moved their ears. but little, and thus gradually lost tne power of movmg them. This would be a parallel case with that of those large and hea ,.y birds, 2 ~ ''fhe Discuses of the Ear,' by J. Toynbcc, F.R.S., IE:GO, p. 12. |
