 By the late 19th century, advances in the sciences of anatomy and physiology, as well as the beginnings of an appreciation of the germ theory of disease, had reduced the morbidity and mortality of this operation to a more acceptable rate.Also in the late 19th century, advances in endoscopic instrumentation had improved to such a degree that direct laryngoscopy had finally become a viable means to secure the airway by the non-surgical orotracheal route.Nasotracheal intubation was not widely practiced until the early 20th century.