Mancini followed Agricola's example, and included in this "Riflessioni" (1776) a brief description of the vocal organs. But Mancini made no attempt to apply this description in formulating a system of instruction. He recommends the parents of a prospective singer to ascertain, by a physician's examination, that the child's vocal organs are normal and in good health. He also gives one mechanical rule, so obvious as to seem rather quaint. "Every singer must place his mouth in a natural smiling position, that is, with the upper teeth perpendicularly and moderately removed from the lower." Beyond this Mancini says not a word of mechanical vocal management. There is no mention of breathing, or tone reflection, or laryngeal action. Although Mancini borrowed his description of the vocal organs from Ferrein, his notion of the mechanics of tone-production was very crude. "The air of the lungs operates on the larynx in singing exactly as it operates on the head of the flute." Voice Culture has passed through three successive periods. From 1600 to 1741 instruction in singing was purely empirical. Ferrein's treatise may be said to mark the beginning of a transition period during which empirical instruction was gradually displaced by so-called scientific methods. This transition period lasted, roughly speaking, till the invention of the laryngoscope in 1855. Since that time vocal instruction has been carried on almost exclusively along mechanical lines. No vocal teacher had ever heard of a problem of tone-production previous to 1741, and indeed for many years thereafter. The earlier masters were not aware of any possibility of difficulty in causing the voice to operate properly. Their success justified their ignoring of any mechanical basis of instruction; but even of this justification the later masters of the old school were only dimly conscious. They builded better than they knew. When any teacher of the transition period was called upon to explain his manner of imparting the correct vocal action he was at once put on the defensive. No champion of the imitative faculty could be found. This lack of understanding of the basis of the empirical method, on the part of its most intelligent and successful exponents, was the first cause of the weakness of this method against attack. Another source of weakness in the hold of empirical systems on the vocal profession was seen in the generally high intellectual standard of the more prominent teachers. These masters gladly accepted the new knowledge of the basis of their art, offered them in the description of the vocal organs. Thoroughly conversant with every detail of the empirical knowledge of the voice, the masters of the transition period were well prepared to understand something of the mechanical features of tone-production. By their auditory and muscular sensations of vocal tone they were able, to their own satisfaction at least, to verify the statements of the anatomists.