One of the most recent authoritative writers on voice culture, Dr. Mills, speaks at length of the necessity of guiding the voice by the sense of hearing. "We cannot too much insist on both speaker and singer attending to forming a connection between his ear and his mouth cavity. He is to hear that he may produce good tones, and the tones cannot be correctly formed if they be not well observed. To listen to one's self carefully and constantly is a most valuable but little practised art. The student should listen as an inexorable critic, accepting only the best from himself." Dr. Mills touches on the psychological features of the connection between voice and ear. "There can be no doubt that the nervous impulses that pass from the ear to the brain are of all sensory messages the most important guides for the outgoing ones that determine the necessary movements." Summing up the matter of ear-training and vocal guidance Dr. Mills says: "The author would impress on all students of music, and of the voice as used in both singing and speaking, the paramount importance of learning early to listen most attentively to others when executing music; and above all to listen with the greatest care to themselves, and never to accept any musical tone that does not fully satisfy the ear." (_Voice Production in Singing and Speaking_, 1906.) One more citation from Mrs. Rogers must suffice. "And now, in conclusion, let me once more remind the singer that in practising these and all other vocal exercises the ear is the only safe guide." Given a fine natural voice and a trained musical ear, skill is acquired in the use of the voice by the repetition of effort. The only necessity is for the singer to have a clear mental conception of the effects to be obtained, and to listen attentively to the voice. With each repetition of an exercise, whether on sustained tones, scale passages, crescendo and diminuendo, or whatever else, the voice responds more smoothly and accurately to the mental demand. Each time the student practises the exercise he listens to the tones and notes how they differ from the desired effect; he strives the next time to correct this departure. Psychological principles verify the proverb that practice makes perfect. This is true of all complex activities. Through repeated performance the muscles, or rather the motor-nerve centers, become habituated to complex activities. Coordinations gradually become perfect and automatic because the nerve impulses naturally tend to take the well-worn paths. To this rule the voice is no exception. Practice makes perfect, with the voice, as with every other muscular activity.