NASMYTH'S RESEARCHES ON TIIE TEETH.
THIS volume, though forming of itself a complete treatise on the subject it embraces, is the introductory part of a greater work on the teeth, about to be produced by Mr. NASMYTIL The part already published is the " Historical Introduction ; " in which the author gives a view of the labours of physiologists in investigating the nature and structure of the teeth, from the time of ILPPOCRATES to the present day. The work, when completed, must necessarily be of considerable magnitude ; and the minuteness of its details will of course adapt it more to the perusal of the natural philosopher and the professional man than to that of the general reader. But this intro- ductory volume gives a popular and curious view of the existing state of knowledge, or rather of ignorance, respecting organs which perform such important functions in the animal economy, and of which the diseases and derangements may be ranked among the most distressing of the minor miseries of human life. Till we read
this volume, indeed, we were by no means aware that the physiology of the teeth is so entirely in its infancy as it really appears to be : and we no longer wonder at the little that dentists can do in al- leviating the pangs of toothache, when we find that they are ig- norant of the composition and structure of the substances they have to deal with, and that the practice, consequently, of the most emi- nent among them is little better than empirical. To show the little progress made in dental science and dental practice, it is enough to compare the doctrines of AMBROSE Paid:, a famous physician of the sixteenth century, with those of the illustrious JOHN HUNTER, two hundred years later. PARE believed that the teeth continued to grow during the whole life of the animal ; "for otherwise," he says, "by the continual use of chow- lag, they would be worn and wasted away by one another:" and in proof of this opinion, he adds—" You may perceive this by any that have lost one of their teeth ; for that which is opposite to it becomes longer than the rest, because it is not worn by its oppo- site." PARE also thought that the sense of taste resided not only in the tongue but in the teeth. His treatment included the thrust- ing of' a hot iron into the roots of the teeth ; a remedy which, the writer of this can testify from woful experience, is not yet entirely exploded, having been nearly driven frantic front "the burning of a nerve" by the hands of a respectable dentist. Jona HUNTER sanctions such practices as extractieg a decayed tooth in order to boil and replace it, cauterizing exposed nerves, burning the ear with a hot iron to cure the toothache, &c. ; practices which have generally given way to gentler if not much more efficacious treat- ment. Jona Huyrea also adopted AMBROSE PARE'S notions re- specting the transplantation of teeth.
" The art of transplanting teeth," says Mr. Nassirrn, "which he (John Hunter) illustrated by some very curious experiments, has been since adopted with very injurious and even fatal consequences, but is now, I believe, almost en- tirely abandoned by all practitioners at home and abroad. A persuasion, how- ever, seems still to linger in the minds of many, that there is a possibility of its being practised without any ill eGets. The indifference with which many practitioners still see dead teeth remaining in the mouths of their patients, as well as sundry unwarrantable measures, may be traced to doctrines promulgated by no less an authority than Hunter. But sixty years have now elapsed since he wrote ; and the profession is surely justified in demanding a vast improve- ment in the acquirements of the practitioner who devotes himself to the care of these organs."
Passing over several inquirers, we come to ROUSSEAU, p disciple of CUVIER, who published a work on the teeth in 1827, and whose labours Mr. NASNIITII considers as very valuable. ." In regard to the accidents which the teeth experience, he attaches con- siderable importance to the cracking of the enamel by rapid alternations of beat and cold ; and cites an old adage, that 'a glass of wine drunk immediately after soup draws a crown from the pocket of the physician and puts it into that of the dentist.'
" Caries of the teeth, according to this author, is simply ulceration. Many causes, both external and internal, predispose to this malady, as a scrofulous or scorbutic diathesis, the humidity or particular character or the atmosphere, the nature of the water which is drunk, &c. The latter causes are supposed to operate in the province of Caux, in France, and in the neighbourhood of Beauvais, in Picardy, where the greater part of the inhabitants have the two centre incisors of the upper jaw decayed ; after these the laterals begin to be affected, and so much so that by the time the individual has arrived at the age of thirty he has in general lost almost all his teeth. Rousseau is unable to decide whether this results from the air, the water, or from the immense quan- tity of apples which are consumed in these parts. He remarks, that the inha- bitants of large cities are most subject to the decay of the teeth—that the dog, the faithful companion of man, in good or bad fortune, is often attacked by it; and that the cat, which inhabits our houses, is equally liable to it.' Savage tribes, on the contrary, appear to retain their teeth in health, though worn. "Carnivorous animals -have very healthy teeth: in the savage state, indeed,
time appears to effect no change in them, except that by degrees they become worn down."
It is only within a very recent period that much light has been thrown upon the physiology of the teeth, by the labours of Pro. fessor RETZIUS of Stockholm; who, in 1837, published an interest- ing series of microscopic investigations on the structure of these organs not only in man but in many other animals. Of these in- vestigations Mr. NASMYTH gives a detailed and most instructive analysis: and he also gives an account of the labours of' PURKINJE, MULLER, RASCHKOWs and of many curious and valuable facts lately discovered by these modern inquirers. The general result of their investigations (especially those of RETZIUS) seems to show the existence of a system of innumerable minute tubes or vessels which penetrate the body of the tooth in every direction, ramifying and uniting with each other, and through which certain fluids circu- late. At the same time, the "tubular system," as it has been called, cannot as yet be held as completely established. In his examination of it, 'Mr. NASMYTII shows that it is liable to various objections, or, at least difficulties which require to be removed: and the nature and peculiar functions of the fluids, the circulation of which through the substance of the tooth appears essential to its vitality, remain unknown. It can hardly be doubted, however, that we are arrived at the threshold of discoveries which will place our knowledge of the teeth more on a par with that which we possess of the other parts of the animal frame. Mr. NASMITII says, that he has been still further induced to publish the researches of Rawzius, from having himself made numerous observations and experiments on the same subjects, which, he hopes, will be found to illustrate some of them, and to carry out others to very interest. ing and original conclusions. These will be embodied in the sequel of his work.
The study of odontology is important, not only as the means of alleviating some of the sorest ills which flesh—or rather bone—is heir to, but as a powerful instrument in the bands of the natural historian and geologist. The teeth retain their form and consist. ency for ages after every other part of the animal body is resolved into dust; and no part of the labours of CUVIER are more curious and interesting than the conclusions he has drawn ftoin this source as to the living creatures with which the terraqueous globe has been peopled at different wras of its existence. "Time importance of odontology in a zoological and geological point of view," Mr. Nasmrrn says, "has induced me to form as complete a collection as possible of microscopic preparations of the teeth of the various classes, both living and extinct, of the animal kingdom. From these I intend, in the course of the present work, when treating of the structure of the teeth, to make a selection calculated to serve as an index of the type of any animal,"
This volume is agreeably written, combining scientific precision with popular clearness.
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