“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.[289] 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.