There are cogent reasons for the affinity of the vocal node for certain fixed positions on the cords. They can be explained by the trick of the vibrating string and bit of paper. If the paper is laid upon the string at a certain point, it will be flirted away; while at another chosen point it will slip unagitated to the floor. Inasmuch as the vocal cords are subject to the same laws of vibration, the lesson drawn from the string and the bit of paper applies to them, the node taking the place of the paper. Note, however, the difference. The string is single, and there is no attrition. If there were two strings, the bit of paper might be caught and twisted in the miniature whirlwind of opposing vibrations. But the vocal cords are wedded in phonation, and by their attrition the node is formed. Very often strands of tough mucus appear spanning the chink or slit between the cords when they are drawn up in tone-production. The presence of these bands of mucus is an assured precursor of the node. Often they indicate the existence of a node which is hardly perceptible through the laryngeal mirror. The mucus is nature's effort to relieve the attrition, and so to ease the inflammation at the point of difficulty. The obstinacy with which the nodes caused by vocal disaster thus form in the anterior and middle third of the cords may be explained as owing to the presence in the vocal cords of a point which may be called the centre of resistance for the intrinsic muscles, and indicates that they are caused, in the majority of cases, by undue and improper muscular effort in tone-production. Consequently, the necessity for the most painstaking care on the singer's part to avoid singing under unfavorable conditions. A trifling over-exertion at an afternoon rehearsal in a cold hall, too much talking on the train, a bad night's rest in a sleeper berth, all may conspire to weaken the voice for the time and lay it open to attack. Under such circumstances, particularly, it is necessary for the vocalist to exercise large discretion and to aim for a conservative middle course, and especially so in a preliminary rehearsal. Another cause of the node is a lack of cordal coördination. Were the human form perfect, both cords would be equally strong. As a matter of fact, in my own experience, I have found that the major portion of nodal formations appear on the left cord, indicating that it is the weaker. The fact that one cord is slightly lax while the other vibrates at full tension along its face causes trouble. Another source of difficulty is subglottic, owing to inflammation of the mucous membrane in the trachea, which extends upward and involves the cords. The inflammation, passing upward, may easily affect the voice. Such inflammation is discovered by a tickling sensation in the trachea, causing a dry, harsh cough about the third day after a cold has found lodgment "in the head," as the phrase goes.