Chapter Xxvii: Cure of Teeth Affected by Warm, Painful Disease,

according to Adamantius the sophist.

Chapter XXIX: Cure of teeth affected with pain from humidity.

Chapter XXXI: Cure of teeth affected by pain from dryness, according to Adamantius the sophist.

Chapter XXXII: Cure of teeth affected by pain from heat and humidity.

Chapter XXXIII: Cure of decayed teeth, according to Galen.

It appears very clear, therefore, from the great analogy existing between the headings of all the above-mentioned chapters, that the titles referred to by Geist-Jacobi have not at all the historical importance and significance that he attributes to them, and that the same have been formulated by Ætius himself. To argue from such titles that Adamantius was the author of a book on dentistry is not only inadmissible, for all the reasons already given, but also because if it were allowable to reason with such lightness, it might also be stated—by arguing from the title of Chapter XXXIII—that Galen was the author of a monograph on the treatment of dental caries; a thing which is absolutely untrue. Consequently, the beginning of odontologic literature cannot be traced back to Adamantius, but, as Dr. Geist-Jacobi would have it, to an author much less ancient, that is, to Walter Hermann Ryff, or, if it is preferred, even to the anonymous writers of the odontologic compilations which appeared in Germany at the end of the fifteenth century.

ANDREAS VESALIUS. We must now speak of Andreas Vesalius, an extraordinary man, who by his genius infused new life into medical science, and who, although he gave but little attention to dental matters, yet fully deserves a place of honor in the history of dentistry; for this, like every other branch of medicine, received great advantage from his reforming work, which broke down forever the authority of Galen, thus freeing the minds of medical men from an enslavement which made every real progress impossible.

Andreas Vesalius was born at Brussels, December 31, 1514. He studied at Louvain and then at Paris, where at that time great scientists taught, and among others the celebrated anatomist Jacques Dubois, generally known by the Latinized name of Sylvius. The latter, a great admirer of Galen, whose anatomical writings served as texts for his lectures, became jealous of the young Belgian student, who was his assistant, and who gave undoubted proofs of great genius, and of extraordinary passion in anatomical research. Vesalius often defied the greatest dangers in order to obtain corpses either from the cemetery of the Innocents or from the scaffold at Montfaucon. He soon surpassed his most illustrious masters, and at only twenty-five years of age published splendid anatomical plates, which astonished the learned. He acquired also great renown as surgeon, and in this capacity he followed the army of Charles V in one of his wars against France. After having been professor of anatomy in the celebrated University of Louvain (Belgium), he was invited by the Venetian Republic to teach in the University of Padua, which, through him, became the first anatomical school in Europe. Yielding to the requests of the magistrates of Bologna and Pisa, he also taught in those famous universities, before immense audiences.

Before Vesalius, Galen’s anatomy had served as the constant basis for the teaching of this science. Although even from the end of the fifteenth century dead bodies were dissected in all the principal universities, the teachers of anatomy always conformed, in their descriptions, to those of Galen, so that the authority of this master, held infallible, prevailed even over the reality of facts.

Vesalius, for the first time, dared to unveil and clearly put in evidence the errors of Galen; but this made him many enemies among the blind followers and worshippers of that demigod of medicine. Europe resounded with the invectives that were bestowed upon Vesalius. Among others, there rose against him Eustachio at Rome, Dryander at Marburg, Sylvius at Paris, and this last did not spare any calumny that might degrade his old pupil, who had become so celebrated. In spite of this, the fame of Vesalius kept on growing more and more, so much so that Charles V called him to Madrid, to the post of chief physician of his Court, a place which he kept under Philip II, also after the abdication of Charles V. The good fortune of Vesalius, unhappily, was not to be of long duration. In 1564 a Spanish gentleman died, in spite of the care bestowed upon him by Vesalius, and the illustrious scientist requested from the family, and with difficulty obtained, the permission to dissect the body. At the moment in which the thoracic cavity was opened the heart was seen, or thought to be seen, beating. The matter reached the ears of the relations of the deceased, and they accused Vesalius, before the Inquisition, of murder and sacrilege; and he certainly would not have escaped death except by the intervention of Philip II, who, to save him, desired that he should go on a pilgrimage to the Holy Land, as an expiation. On his return, the ship which carried Vesalius was wrecked, and he was cast on a desert beach of the Isle of Zante, where, according to the testimony of a Venetian traveller, he died of hunger, October 15, 1564.

Vesalius left to the world an immortal monument, his splendid treatise on Anatomy, published by him when only twenty-eight years of age, and of which, from 1543 to 1725, not less than fifteen editions were issued. The appearance of this work marked the commencement of a new era. The struggle between the supporters of Galen and those of Vesalius rendered necessary, on both sides, active research concerning the structure of the human body, so that anatomy, the principal basis of scientific medicine, gradually became more and more perfect, and, as a consequence of this, as well as of the importance which the direct observation of facts acquired over the authority of the ancients, there began in all branches of medicine a continual, ever-increasing progress, which gave and still gives splendid results, such as would have been impossible under the dominion of Galenic dogmatism.

In the great work of Vesalius the anatomy of the teeth is unfortunately treated with much less accuracy than that of the other parts of the body. However, his description of the dental apparatus is far more exact than that of Galen, and represents real progress. The number of the roots of the molar teeth (large and small) is indicated by Galen in a very vague and inexact manner, since he says that the ten upper molars have generally three, sometimes four roots, and that the lower ones have generally two, and rarely three. Vesalius, having examined the teeth and the number of their roots in a great number of skulls, was able to be much more precise. In regard to roots, he makes, for the first time, a very clear distinction between the premolars next to the canine (small molars) and the other three, and says that the former in the upper jaw usually have two roots, and in the lower, one only, whilst the last three upper molars usually have three roots and the lower ones two. As everyone sees, these indications are, in the main, exact.

Other important facts established by Vesalius are as follows:

The canines are, of all the teeth, those which have the longest roots. The middle upper incisors are larger and broader than the lateral ones, and their roots are longer. The roots of the last molars are smaller than those of the two preceding molars. In the penultimate and antepenultimate molars, more often than in the other teeth, it sometimes happens that a greater number of roots than usual are found, it being not very rare to meet with upper molars with four roots, and lower ones with three. The molars are not always five in each half jaw; sometimes there are only four, either on each side, or on one side only, in only one jaw or in both. Such differences generally depend on the last molar, which does not always appear externally, remaining sometimes completely hidden in the maxillary bone, or only just piercing with some of its cusps the thin plate of bone which covers it; a thing which Vesalius could observe in many skulls in the cemeteries.

In regard to the last molar, the author speaks of its tardy eruption and of the violent pains which not unfrequently accompany it. The doctors, he adds, not recognizing the cause of the pain, to make it cease have recourse to the extraction of teeth, or else, attributing it to some defects of the humors, overwhelm the sufferer with pills and other internal remedies, whereas the best remedy would have been the scarification of the gums in the region of the last molar and sometimes the piercing of the osseous plate which covers it.

This curative method, of which no one can fail to recognize the importance, was experimented by Vesalius on himself, in his twenty-sixth year, precisely at the time that he had just begun to write his great treatise on anatomy.

The existence of the central chamber of the teeth appears to have been unknown to Galen, as he does not allude to it in the least. Vesalius was the first to put this most important anatomical fact in evidence. He expresses an opinion that the central cavity facilitates the nutrition of the tooth. He says, besides, that when a hole is produced in a tooth by reason of acrid corrosive humors, the corrosion, when once the internal cavity is reached, spreads rapidly and deeply in the tooth, owing to the existence of the said cavity, and sometimes reaches even the end of the root.

In the chapter in which Vesalius treats of the anatomy of the teeth (Chapter XI, p. 40), two very well-drawn figures are found, one of which represents a section of a lower molar, showing the pulp cavity and its prolongation into the two root canals. The other represents the upper and lower teeth of the right side, in their reciprocal positions, and shows very clearly their general shape, the length of their roots, and the number of these.

The changes which take place in the alveolus, after the extraction of a tooth have not escaped the notice of Vesalius. He says that after an extraction the walls of the alveolus approach one another, and the cavity is gradually obliterated.

Aristotle had affirmed that men have a greater number of teeth than women. Vesalius declares this opinion absolutely false—although, after Aristotle, it has been repeated by many other ancient writers—and says that anyone can convince himself that the assertion of Aristotle is contrary to the truth, as it is possible for everybody to count his own teeth.

In spite of this, we find the above-mentioned error even in writers subsequent to Vesalius; for example, in Heurnius (professor at Leyden toward the end of the sixteenth century), who expresses an opinion that rarely do women have thirty-two teeth, like men.

We find but little in Vesalius concerning the development of the teeth. He, indeed, made some observations and researches on this point, but these, from their insufficiency, led him to quite mistaken conclusions. The teeth of children, he says, have imperfect, soft, and, as it were, medullary roots; and the part of the tooth which appears above the gums is united to the root, so to say, as a mere appendix, after the fall of which there grows from the root the permanent tooth. This error arose in the mind of Vesalius from observing that when children lose their milk teeth, these have the appearance of a kind of stump, as if the root had actually remained in the socket. Besides this, he had observed with what facility the milk teeth fall out; and he here calls to mind that, when about seven years old, he himself and his companions used to pluck out their loosened teeth, and especially the incisors, with their fingers, or with a thread tied around the tooth. The softness of the dental roots in children, the easy fall of the milk teeth, and the want of the lower part of the roots in these, must have raised the idea in his mind that the roots of the milk teeth remained in the socket, and that the upper part of the temporary teeth, instead of being a continuation of the root, was joined to this as a simple appendix, and in a very weak way, as though designed to remain in place for a limited length of time only.

In Vesalius is found a dental terminology—Latin, Greek, Hebrew, and Arabic—which affords some interest. The incisors are called in Latin incisorii, risorii, quaterni, quadrupli; and the two middle incisors have been denominated by some authors duales. The canines are called in Greek kynodontes, which means the same as the Latin canini, dog’s teeth. In Latin they have been also denominated mordentes, and by some also risorii, a name which by others is given to the incisors, as we have already seen. The molars have also been called in Latin maxillares, paxillares, mensales, genuini. But some authors give this last name only to the last molars, or wisdom teeth, dentes sensus et sapientiæ et intellectus. These teeth have also been called serotini (that is, tardy), ætatem complentes (that is, completing the age, the growth), and also, in barbaric Latin, cayseles or caysales, negugidi, etc.

In the rebellion against the authority of the ancients, Vesalius had a predecessor whose name, deservedly famous, may be recorded here. PARACELSUS (born in 1493 at Maria-Einsiedeln, Switzerland), on being nominated, in 1527, Professor of Medicine and Surgery at Basle, inaugurated his lectures by burning in the presence of his audience, who were stunned by such temerity, the writings of Galen and Avicenna, just as Luther, seven years before, had burnt in the public square of Wittenberg the papal bulls and decretals. The sixteenth century, in its exuberance of intellectual life, was undoubtedly one of the grandest centuries in history; human thought in that glorious epoch shattered its chains, and declared its freedom both in matters of science and of religion.

Paracelsus, a man of powerful genius, but not well balanced in mind, of corrupt morals, and of an unlimited pride, had, notwithstanding these undeniable defects, the merit of beginning a healthy reform in the science and practice of medicine, by substituting the study of nature for the authority of the ancients and by giving a great importance to chemistry, both for the explanation of organic phenomena and for the cure of disease.

It is to be lamented that this man of genius did not contribute in any way to the progress of dentistry. His works have no importance for us. As a matter of mere curiosity we only record here that Paracelsus considered the too precocious development of the teeth as a great anomaly, and regarded as monsters those children who were born with teeth.

GIAN FILIPPO INGRASSIA (1510 to 1580), a distinguished Sicilian anatomist, was one of the first who spoke of the dental germ. He says that the existence of the tooth properly so called is preceded by that of a soft dental substance enclosed in the bone, and which he considers almost as a secretion of the latter.

MATTEO REALDO COLOMBO, of Cremona, a pupil of Vesalius and his successor in the professorship of Anatomy at Padua, added but little, as regards the teeth, to what his master has taught. He combated the erroneous idea that the teeth were formed in the alveoli shortly before their eruption. Having dissected the jaws of many fetuses, and having always observed in them the existence of teeth, he could affirm with every certainty that the teeth begin to be formed in intra-uterine life.

Like Vesalius, Realdo Colombo believed that the permanent teeth were developed from the roots of the milk teeth; and, therefore, he advised the utmost caution in extracting these, since, if the whole root were removed, the tooth would not grow again.

GABRIEL FALLOPIUS (1523 to 1562), the eminent anatomist of Modena, also a disciple of Vesalius, carried out accurate and successful researches in regard to the development of the teeth, and made them known in his book, Observationes anatomicæ, published at Venice in 1562, the year in which he died.

His investigations enabled him to show the falsity of the opinion held by Vesalius, that the permanent teeth are developed from the roots of the temporary ones. He was, besides, the first who spoke in clear terms of the dental follicle.

The teeth, says Fallopius, are generated twice over, that is, the first time in the uterus, after the formation of the jaws, and the second time in extra-uterine life, before the seventh year. The first teeth are, at the time of birth, still imperfect, without roots, completely enclosed in their alveoli, and formed of two different substances; the part with which they must break their way out is osseous and hollowed; the deeper part, instead, is soft and humid and is seen covered with a thin pellicle, a thing which may also be observed in the feathers of birds when they are still tender. In fact, the part of the feather which comes out of the skin is hard and corneous, whilst the part which is embedded in the wings is soft and humid and has the appearance of coagulated blood or mucus. So also in the fetal teeth, the part corresponding to the future root presents itself like coagulated mucus. Little by little this soft substance hardens and becomes osseous, thus constituting the root of the tooth.

Fallopius’ reference to the analogy between the development of teeth and that of feathers was highly important, as a point of departure for embryological researches which showed clearly the real nature of teeth, thus destroying the mistaken idea—held by Galen and many other authors—that these organs were bones.

On coming to speak of the teeth generated in extra-uterine life, that is of the permanent teeth, Fallopius relates having observed that they have their origin in the following manner: A membranous follicle is formed inside the bone furnished with two apices, one posterior (that is to say, deeper down, more distant from the surface of the gums), to which is joined a small nerve, a small artery, and a small vein (cui nervulus, et arteriola, et venula applicantur); the other anterior (that is more superficial), which terminates in a filament or small string, like a tail. This string reaches right to the gum, passing through a very narrow aperture in the bone, by the side of the tooth which is to be substituted by the new one. Inside the follicle is formed a special white and tenacious substance, and from this the tooth itself, which at first is osseous only in the part nearest the surface, whilst the deeper part is still soft, that is, formed of the above-mentioned substance. Each tooth comes out traversing and widening the narrow aperture through which the “tail” of the follicle passes. The latter breaks, and the tooth comes out of the gum, bare and hard; and in process of time the formation of its deeper part is completed.

The author says that his long and laborious researches into the development of the teeth were carried out with great accuracy, and he is, therefore, in a position to give as absolute certainties the facts exposed by him. Indeed, the observations of Fallopius were, for the most part, confirmed by subsequent research. As to the “tail” of the dental follicle, it is identical with the iter dentis or gubernaculum dentis of some authors. Fallopius described it as a simple string, but later on this prolongation of the dental follicle has been considered, at least by some, as the narrowest part or neck of the follicle itself, that is, as a channel through which the tooth passes, widening it, on its way out, and precisely for this reason it has been called iter dentis (the way of the tooth) or gubernaculum dentis (helm or guide of the tooth).

BARTHOLOMEUS EUSTACHIUS, another great anatomist of the sixteenth century, occupied himself in the study of teeth with special interest, and wrote a very valuable monograph on this subject. He was a native of San Severino, Marche (Italy), and a contemporary of Vesalius, Ingrassia, Realdo Colombo, and Fallopius; he died in 1574, after having immortalized his name through many anatomical discoveries and writings of the highest value.

His book on the teeth, Libellus de dentibus, published at Venice in 1563, is the first treatise ever written on the anatomy of teeth, and represents a noteworthy progress in this branch of study.

In this little book—divided into thirty chapters, forming in all ninety-five pages—the author treats with great accuracy and in an admirable manner all that concerns the anatomy, physiology, and development of the teeth.

Eustachius not only treasured up what ancient authors had written on this subject, but he himself made very long and patient researches and observations on men and animals, on living individuals as well as on corpses, and not only on adult subjects, but also on children of every age, on stillborn children and on abortive fetuses.

The macroscopic anatomy of the teeth was brought by him to a high degree of perfection. Very wonderful, among other things, is the accuracy with which he studied and specified in several synoptical tables the number of the roots of molar teeth, and all the variations occurring not only in their number, but also in their form, length, etc.

In Chapter IV, speaking of the means by which teeth are held in their sockets, Eustachius mentions in quite explicit terms the ligaments of the teeth. He begins by saying that the perfect correspondence between the dental roots and the alveoli, both in shape and in size, is one of the elements which contribute to the firmness of the teeth, since the alveolus, being exactly applied, on all sides, to the root or roots of the tooth, causes the latter, by this simple fact, to be fixed in a determined position. Also, the nerves inserted in each single tooth contribute, as was already the opinion of Galen, to the stability of these organs. “There exist besides”—Eustachius continues—“very strong ligaments, principally attached to the roots, by which these latter are tightly connected with the alveoli” (adsunt præterea vincula fortissima radicibus præcipue adherentia, quibus præsepiolis arctissime colligantur). Lastly, says the author, the gums, too, embracing the teeth at their exit from the alveoli, contribute to their firmness. And here Eustachius notes that in the joining of the gums to the teeth there is great analogy to that of the skin with the finger nails; a very proper observation, which makes us almost suppose that the perspicacious mind of Eustachius may have guessed the kindred nature of nails and teeth.

In Chapter XV are related the researches made by the author to ascertain at what period the development of the teeth begins. Here is a passage of this chapter, almost literally translated:

“Hippocrates, before anyone else, wrote that the first teeth are formed in the uterus. Wishing to assure myself thereof, I dissected many abortive fetuses, and by very careful observations I found it to be true that the teeth have their origin during intra-uterine life. Wherefore, the opinion of those who consider that the first teeth are formed from the milk, and those of the second dentition from food and drink, must be declared entirely false. In fact, by opening both jaws of a stillborn fetus, one may find, on each side of each jaw, the incisors, the canine, and three molars, partly mucous and partly osseous, and already sufficiently large and entirely surrounded by their alveoli. Then removing, with a skilful hand, the incisors and the canines, there may be observed a very thin partition only just ossified; and if this be removed with equal care, an equal number of incisors and canines, almost mucous and very much smaller, appear, which, enclosed in special alveoli behind the first, would exactly correspond in position each with its congener, if in both jaws the canine were not resting for the greater part on the next incisor so as almost to hide it.”

As to the molars (by which name also the bicuspids are here meant), Eustachius says that he found but three on each side, and no trace whatever of the others. Nevertheless, he considers it quite probable that the germs of the latter should also exist in the fetus, although so small as to escape observation. He gives many ingenious reasons in support of his mode of thinking, and comes to the general conclusion, that not only the temporary teeth but also the permanent ones have, all of them, their origin during fetal life; a false conclusion simply because too general, and which shows once more how, in biological science, one runs great risk of falling into error whenever one tries to draw too free deductions from observed phenomena.

The researches of Fallopius and Eustachius confirm and complete each other. These two eminent anatomists, who gave great glory to Italy by their immortal discoveries and works, were the first to shed a brilliant light upon the development of the teeth, and thus opened up the way to all subsequent research on odontogeny.

In settling the period in which the formation of the teeth begins, Fallopius was still more successful than Eustachius. His patient investigations showed him that the development of the teeth commences partly in the uterus and partly after birth, which is perfectly true, as was made clear by later embryological researches. Fallopius found in each fetal jaw twelve teeth. In this he agrees perfectly with his contemporary, Eustachius, who, as we have seen a short while ago, found in fetusus, only just born, the incisors, the canines, and three molars for each side of each jaw. Eustachius, however, observed in the fetus the germs of the permanent incisors and canines as well, a thing not noted by Fallopius.

It is not to be wondered at that some discrepancy should exist between the observations of these two eminent anatomists. The researches of which we are speaking are sufficiently delicate and difficult; and even much more recent authors are far from agreeing perfectly, as far as regards the period, in which the development of the teeth begins. Serres, in his Essai sur l’anatomie et la physiologie des dents (Paris, 1817), sustains the view that in the fetus he has observed the germs of all the teeth, both temporary and permanent, while Joseph Linderer (Handbuch der Zahnheilkunde, Berlin, 1842) says that, although he has followed the preparative method indicated by Serres, he could never discover in the fetus the germs of all the teeth. Perhaps, he adds, the time when the development of the teeth begins varies considerably in individuals, just as we remark differences in the time of eruption.

In Chapter XVII of his book, Eustachius speaks of the process of formation of the teeth, which he studied in abortive fetuses, in stillborn children, in children a few months old, and also in kids.

On dissecting a fetal jaw, there may be found on each side, as we have already seen, the incisors, the canines, and three molars, still soft and imperfect, separated from one another by very thin osseous partitions. Each of these teeth is enclosed within a follicle or little bag of a grayish white color, rather more mucous and glutinous than membranous, and in form somewhat like the pod of a vegetable, with the only difference that it shows an opening at one of the extremities, from which the tooth somewhat protrudes, as if it were germinating. The more recent and softer the tooth, the more its follicle has a mucous appearance and differs from the nature of membranes. As it does not adhere to the underlying tooth, it is easy to separate them. As to the tooth, it is at that period of its development partly osseous and partly mucous, since that part which later on projects from the gum soon becomes transformed into a white thin and concave scale, which gives the idea of one of the little cells of a honeycomb. This scale is harder and more conspicuous in the incisors, since these, at this stage, are better formed; the canines are less advanced in development, and the molars still less; and among these latter, those are less developed which are more distant from the canines. The deeper part of the tooth consists of a mucous and tenacious substance, harder, however, than the substance of the follicle, and of a whitish color with a tendency to dark red, translucent, and somewhat brilliant.

Thus, says Eustachius, the teeth present themselves in a human fetus; but he who cannot obtain a human fetus may observe the same things in a kid.

Although the author does not express himself very explicitly, he seems to consider the follicle of the tooth substantially identical with its ligament. “This is at first mucous, but afterward, becoming more consistent, causes the tooth to adhere to the socket and gum very firmly, as if it were glued.”

“As the part of the tooth which comes out of the gum projects from the aperture of the follicle like a gem from its bezel, so—says Eustachius—some believe that the crown of a temporary tooth is a mere appendix, and that the follicle comes out of its concavity through a dividing line which they imagine to exist between this supposed appendix and the remaining part of the tooth. But assuredly those who assert such things show that they have studied the anatomy of the teeth so carelessly that, by this one error, they make manifest their great ignorance together with their great temerity. The line which is observed on the tooth on the part corresponding to the adhesion of the gingival margin and of the dental ligament is very superficial, and after having scraped it away, there does not remain any trace of a division. But apart from this everyone can very easily observe, even in infants, or in kids, that the tooth when ossified does not present any line of division and that the still mucous follicle envelops it freely, and may be easily separated from the tooth; which would not be the case, if the follicle issued from between the tooth and its supposed appendix.”

Thus, Eustachius declares entirely false the opinion already expressed by Celsus, that the permanent tooth grows from the root of the milk tooth. He affirms clearly and decisively that between the external and the radical part of a milk tooth no real division exists, and that the ossification of the tooth, beginning from the crown, proceeds without any interruption right down to the end of the root. If it were true, says he, that in children only the imaginary epiphysis or appendix falls, and that the new tooth is substantially represented by the remaining part of the first, it could never happen, as instead it often does, that the new tooth appears before the first one falls. Besides, between the lower part of the first tooth and the upper part of the second no correspondence exists either in size or shape, as ought necessarily to be the case if the two parts were joined together. This is not all; the lower part of the temporary tooth is perforated, and receives in its interior bloodvessels and nerves, whilst the upper part of the permanent tooth is quite massive and imperforated. How, then, could this second tooth transmit bloodvessels and nerves into the cavity of the first? Again, how could the continuity of these bloodvessels and nerves with their respective branches be possible, if an imperforate body, such as the crown of the permanent tooth, were really interposed?

But what is the use of so many arguments? exclaimed Eustachius. To remove even the slightest doubt and to put an end to any controversy on such a point, only one fact is sufficient, which is revealed to us by anatomical dissection, and that is, that the teeth which appear about the seventh year are not only not united to those which fall at the same period, but cannot even be in contact with them, owing to the presence of a thin osseous partition.

In the following chapter Eustachius speaks of the central cavity of the teeth and of the substance contained in it. In young teeth, he says, the dental cavity is very large, in proportion to the size of the tooth. According to some anatomists, the central cavity of a tooth is coated by a very soft and thin membrane, formed by a tissue of very small vessels and nerves; and besides, this cavity is filled with marrow, like hollow bones. The observations of the author, however, do not agree with these statements. The dental cavity does not contain any fatty substance analogous to the marrow of bones. As to the above-mentioned membrane, Eustachius doubts its existence. The large hollow existing in children’s teeth contains, he says, a mucous substance, somewhat hard, and very smooth at its surface—almost like a cuticle—but which has rather the appearance of a concretion than of a membranous tissue. At any rate, adds Eustachius, if the substance alluded to is made to dry up in the shade, it acquires an appearance not unlike that of a membrane. It is certain, however, that at an early age the substance contained in the dental cavity does not adhere to the walls of the latter after the manner of a periosteum, but is found in simple contact with the same, and can, therefore, be separated from them with the greatest ease.

As years pass by, the dental cavity becomes narrower and narrower, because the substance contained inside the tooth gradually becomes ossified at the surface, adhering to the dental scale previously formed, in the very same manner as the internal or woody part of a tree adheres to the bark. Of the two hard substances which make up a tooth, the outer one is white, tense, and dense, like marble, the underlying one, instead, is somewhat dark, rough, and less compact. To observe accurately the above-mentioned facts, the author advises searching for them, first, in the molar teeth of the ox or the ram, and then in human teeth, and likewise, first in children or in recently born animals, and then in adults.

Chapters XIX and XX are, comparatively speaking, of little importance. In the former the author undertakes especially to examine the opinions of Galen on dental bloodvessels and nerves, and discusses whether it were known to him that these vessels and nerves penetrate into the internal part of the teeth. In the latter, Eustachius speaks of the great difficulties that are encountered in dissecting dental bloodvessels and nerves, and reproves those who, by inaccurate illustrative figures, convey the erroneous idea that these parts are very clearly and easily observable.

In Chapter XXI the author goes on to speak of the best mode of proceeding in order to make successful observation of the small nerves and vessels going to the roots of the teeth. These researches are much more easily made in large animals than in man; and therefore such things as cannot be observed well in the latter must be studied in the former.

In the first place, it is necessary to dissect the lower jaw; and after having done so several times, with all the accuracy required in making researches of this kind, one may proceed to study the dental nerves and vessels of the upper jaw, which is much more difficult. Having opened up the inside of the lower jaw, one observes a cavity full of marrow, and within this a nerve enclosed entirely in its own sheath. Having removed the marrow, and opened the sheath lengthwise, one perceives that the nerve therein enclosed is constituted (analogous to what may be observed in the large nerves of the limbs) by several nervous strings, and that among these runs a comparatively large artery, besides small vascular branches of minor importance. If one then removes the sheath from the bone, together with the nerve and the vessels contained in it, raising it very gently, one sees, issuing therefrom, some very slender fibers, on the nature of which it is, however, difficult to pronounce; and, considering their thinness, one can hardly conceive that they are composed of three different elements, that is, of small nervous, arterial, and venous twigs. At any rate, the author admits that this may be so. On arriving at the lesser teeth, the nerve and the artery that accompanies it divide into two branches, one of which traverses the opening presented by the bone at that point (mental foramen), and is destined to the lower lip; the other directs its course toward the roots of the incisors. The small twigs which penetrate into the roots of the incisor and canine teeth are less slender than those which enter the roots of the molars, and are easily to be seen not only in large animals, but also in man. If the tooth of an ox or that of a ram be split through the middle, the mucous substance contained in the interior is seen to be traversed by small bloodvessels; and one perceives, besides, certain fibers, which are probably nerves. All these things, says Eustachius, I have observed many times in different animals, in some cases more, in others less distinctly. But it is an exceedingly difficult thing to follow the single twigs, of which we have spoken, from their origin to their insertion, or, vice versa, from their insertion to their origin. And so, adds the great anatomist, being able to observe but a small part of the things I should like to see, I find myself compelled, in my perplexity, to supply by the aid of ratiocination the deficiency of the senses. I therefore maintain that the interior part of a tooth is susceptible of experiencing pain accompanied by a feeling of pulsation (a fact already mentioned by Galen), because a nerve and an artery penetrate into it. In the ox the penetration of bloodvessels into the roots of the teeth can be more readily ascertained than in man. It may be admitted that the same occurs in the human teeth; and this, for the reasons already given, and also because only by admitting the existence of an artery within the cavity of the tooth can be explained the copious flow of florid red blood from a decayed tooth, which has, in some cases, been known to imperil the life of a patient. And I myself, says Eustachius, have observed with my own eyes an accident of this kind.

The author then passes on to speak of the eruption of the teeth, but the data with which he furnishes us are neither very precise nor very exact.

Eustachius, without declaring himself for or against it, cites, in this chapter, the opinion of those who believe in the possibility of a third dentition in old people. He returns to this subject in the last chapter but one of his book, which treats of dental anomalies: “Ali,” says he, “testifies to old persons having had all their teeth renewed. This has been derided as chimerical by medical men of later date, or at least only admitted under the condition that such teeth be of a nature completely different from the first.”

Our teeth, says the author, grow old together with us, and toward the term of life they abandon us, a fact which also distinguishes them from the other bones. When, however, it occurs, through illness, that the teeth are extracted or fall out spontaneously before the period of old age, the alveoli become filled up with a bony substance; and in addition the two osseous scales of the maxillary bones approach one another and unite together in such a manner as to form a sharp margin, every vestige of a cavity being obliterated.

Speaking of the nutrition and growth of the teeth, Eustachius says that—given the existence of the dental nerves and bloodvessels—it is not difficult to explain how the teeth are nourished, grow, live, and feel. He therefore rejects the opinion of those who held that the teeth of the lower jaw derived their nourishment from the marrow contained within this bone, and that those of the upper jaw received it from a humorous substance similar to marrow, existing in the large cavity of the upper maxillary bone. Against the supporters of this opinion Eustachius raises, among others, the following objections, viz., that the marrow of the inferior jaw does not in any way touch the teeth, so that such a mode of nourishment cannot be imagined, and that it is completely erroneous that the large cavity of the upper maxillary bone contains a humor similar to marrow. This passage of Eustachius’ book gives clear evidence that he was well acquainted with the maxillary sinus, described a century later by the English anatomist, Highmore, who gave it his name. The existence of this cavity was, besides, already known before the time of Eustachius.

The author also says that those who believe that the internal cavity of the teeth contains marrow, and that this serves to nourish them, are grossly deceived.

In the same chapter, Eustachius confutes an opinion, at that time generally diffused and put forward for the first time by Aristotle, viz., that the teeth grow throughout a whole lifetime. In the senile age, he says, the teeth become impaired still earlier than the other organs. They become thinner by deficiency of nourishment, and, at the same time, discolored; the incisors and canines, as they waste away, come to be also less sharp than they were; and the molars, losing their tubercles or cups, become levelled down and smooth. If, notwithstanding the evident wearing out of the teeth, they seem sometimes to grow longer, this appearance is not to be trusted, for it happens not unfrequently that the teeth appear to have grown longer simply by atrophy of the gums, or also because some humor or other morbid substance pushes them outward.

As to the sensibility of the teeth, Eustachius is of the opinion that these organs possess, besides the sensibility to pain, two other species of sensibility; for, following the ideas of Galen, he also holds that the teeth together with the tongue partake in the sense of taste; and he further considers the disagreeable sensation known as setting on edge of the teeth, as a species of tactile sensation peculiar to these organs.

But in which part of the tooth does the faculty of feeling reside?

Among the authors previous to, or contemporaries of, Eustachius, some affirmed that the sensibility of the tooth resides in the pellicle which lines its inside cavity, others in the membrane which, like periosteum, clothes the root of the tooth, others in both these parts. Eustachius does not show himself more partial to the one than the other of these opinions; he is, however, firmly persuaded that the hard substance of the tooth is also endowed with sensibility. Though it is not easy to explain how this may be, he considers it probable that the nerve, fraying itself out inside of the tooth in minute filaments at the time when the substance of the tooth is still soft and mucous, intermixes intimately with it, thus communicating to it the faculty of feeling, which then persists in it, even after the ossification of the tooth. Such an hypothesis is certainly worthy of the lofty intellect of Eustachius, and has in itself, so it seems to me, something of truth.

In the two following chapters, the author speaks in a masterly and admirable manner of the functions of the teeth and of their utility.

Among many other true and interesting observations, he remarks that by the loss of their teeth even the most powerful dogs become cowards.

Besides what concerns the human teeth, excellent notions of comparative anatomy, above all in what regards the monkey, the dog, and the ruminants, are to be found in this little but most precious book of Eustachius.

The teeth, says he, are not equally hard in all animals, and many ancient authors have affirmed that ferocious animals have much harder teeth than tame ones.