Development of Respiratory Organs
The development of the respiratory organs. A, is the esophagus of a chick on the fourth day of incubation, with the rudiments of the trachea on the lung of the left side, viewed laterally; 1, the inferior wall of the esophagus; 2, the upper portion of the same tube; 3, the rudimentary lung; 4, the stomach. B, is the same object seen from below, so that both lungs are visible. C, shows the tongue and respiratory organs of the embryo of a horse; 1, the tongue; 2, the larynx; 3, the trachea; 4, the lungs, viewed from the upper side.