This author says that the teeth of the Ethiopians and of the Indians are generally whiter than those of the northern peoples, but that those of the Indians soon lose their primitive whiteness by reason of the widely diffused habit of chewing betel-nuts. Fredericus refers to an experiment which, according to him, demonstrates the “sympathetic relations” between the teeth and the ear (whilst in reality it only proves the facility with which sounds may be transmitted through solid bodies). “If, by night,” says he, “one holds tightly between one’s teeth the end of a stick, stuck upright in the ground, one hears the footsteps of a person approaching from afar much more easily.” Through the researches of three great men, Marcello Malpighi, Friedrich Ruysch, and Antoni van Leeuwenhoeck, an altogether new science arose in the seventeenth century, viz., histology, or the anatomy of the tissues, whose revelations contributed not a little to the development of modern odontology. MARCELLO MALPIGHI (1628 to 1694), the celebrated Italian anatomist, was the initiator of microscopic observations on the tissues, and is, therefore, justly considered the founder of histology, within the range of which he made most important discoveries.[355] FRIEDERICH RUYSCH (1638 to 1731), professor at Amsterdam, rendered his name illustrious particularly by bringing to a high degree of perfection the processes of anatomical preparations and of embalming.[356] His magnificent injections, carried out with a method of his own invention, enabled him to trace the most minute vascular ramifications and to demonstrate the existence of capillary vessels in parts where their presence had as yet never been suspected. Ruysch studied accurately the anatomical constitution of the teeth, and especially their vessels. He called attention to the membrane which lines the maxillary sinus, and discovered in it a number of bloodvessels.