Substance of a lecture on the functions of the mouth, and the structure of recent and fossil teeth / [Alexander Nasmyth].

  • Alexander Nasmyth
Date:
[1840]
Catalogue details

Licence: Public Domain Mark

Credit: Substance of a lecture on the functions of the mouth, and the structure of recent and fossil teeth / [Alexander Nasmyth]. Source: Wellcome Collection.

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    o valuable, curious, and appropriate prepara¬ tions. The teeth of the crocodile and shark are so often broken and destroyed in their ferocious combats, that nature has provided them with many successive and complete sets of teeth, which may be brought into use as required. Other teeth, as those of the pike, become anchylosed, or fixed firmly and immoveably to the jaw, so that they cannot be removed in even their most violent encounters. Specimens of both of these were exhibited. The lec¬ turer then shewed, in an admirable manner, that activity and energy, in the character of an animal, were always accompanied by rapidity of assimilation and strength in the assimilative apparatus. This was exemplified by comparing the fish just mentioned with the whale—a toothless animal—which, floating at ease on the surface of the deep, sucks in diminutive, unresisting prey. With the same view, birds of prey were compared with the grass-eating goose—beasts of prey with herbivorous animals. The truth of these observations could be demonstrated even in the human species : a well-developed mouth, furnished with strong and powerful teeth, capable of perfectly performing the function of mastication, introduces the food into the stomach well prepared for complete digestion, and, of course, accele¬ rates that process which thus duly nou¬ rishes the system, and obviates all re¬ dundancy and oppression : under such circumstances, the osseous system is also well knit, and the chest well developed— all in consequence of the activity induced by the due and complete performance of the function of digestion. The character of the animal, the lecturer ingeniously said, is often beautifully expressed by the mere apparatus of the jaw. Thus the power¬ ful teeth in the front of the mouth of the horse, both above and below, indicate his celerity; whilst the more sluggish ox has comparatively weak teeth in the upper jaw, and none below. The maxillary ap¬ paratus of the herbivorous animals amongst the mammalia shews that they are destined to be the drudges of mankind. In man we observe none of the manifestations of extreme activity on the one hand, or of sluggishness on the other, which charac¬ terize the different orders of lower animals ; but in him the faculties which are distri¬ buted in various degrees to the other species are so concentrated as to produce the most complete harmony, and the most ex¬ tensive range of action ; in like manner his teeth are the most harmoniously de¬ veloped and perfectly formed. The limits of a single discourse being altogether in¬ sufficient for tracing the various parts of the mouth in the progress of their develop¬ ment, the lecturer now selected the teeth for the exclusive consideration of his audience. All teeth, he said, may be re¬ garded as cones or wedges, of which there may be one or more in each tooth more or less acute. The grinders of herbivora con¬ sist originally of several wedges or cones. The front teeth or incisors are generally wedge-shaped. The canines are generally simple cones ; and the grinders of the car¬ nivora present a combination of the latter. Sometimes the teeth are composed of a series of cones or wedges bound together at their bases, as in the grinders of the elephant, in the beautiful little incisors of the flying lemur, sus oethiopicus, and others. The only exception to the cone or wedge-shape, in the construction of teeth, is presented by those of several fishes, such as the wolf-fish, the myliobatis, &c., which are in the form of pavements of various kinds, and which are for the pur¬ pose of breaking down the hard shells by which the bodies of their prey are covered and defended. The simplest form of per¬ fect teeth is that in the human subject. It is a remarkable fact that no other con¬ formation of mouth than that of man could admit at once of perfect articulation, and of a proper mastication of food. “ The mouth,” said Mr. Nasmyth, “ may be considered to fulfil the most essential part in the animal and intellectual life of man; for it is not only in him, in com¬ mon with other animals, the essential and original element of the apparatus of assimilation, but it is also the organ of in¬ tellectual expression, and as such is equally indispensable to the existence of the race; it is also the grand agent for the improvement of its condition, and for the communion of social life. There is a most exalted contrast, and, at the same time, an evident fitness, in the circumstance that the same organ which is the instrument in the hands of the Almighty to build up the wondrous and upright structure of his own image, is the very one he has also chosen to sound his praises, and make him known on earth.’’ The lecturer next proceeded to treat of the development and structure of the teeth ; and this portion of his subject was illus¬ trated by a variety of splendid diagrams. The teeth may be said to be formed by a re-duplication of the mucous membrane of the month called the pulp, which Mr. N. has discovered to be composed of cellules or vesicles, in which the ossific matter of the ivory is deposited : the ivory is, therefore, neither more nor less than ossified pulp. Of the reticular or formative surface of the pulp, the lecturer here exhibited some particularly interesting coloured drawings. With respect to the ivory, the doctrine of Liewenhoek, that it is tubular, has lately been revived; but Mr. Nasmyth stated