Frozen Sections of a Child

e rib below it. The manubrium is divided in its lower half. The second rib, bone and cartilage, continues nearly horizontally from the point at which it is divided to its insertion. The cartilages of the following ribs, excepting the last two, have both a falling and a rising portion. Braune states that at about this level the antero-posterior diameter of the chest equals one- third of its breadth, while in the new-born child it is one-half. In a man of fifty, however, he found the proportion 1 to 2.5, which is very nearly that of this subject. That, however, was probably an individual peculiarity, and the shape of the thorax at three, seems to be intermediate between that of the infant and the adult. A great deal more lung-tissue is seen here than in the preceding plate. The pleurae are still far apart, not quite reaching the borders of the sternum. Between them we have the anterior mediastinum filled with areolar tissue, bounded by the sternum in front and the aorta and vena cava behind. Between the latter and the trachea is found a large part of the thymus, which is peculiarly situated, as it is not common for it to extend so far back. It is seen again in Plate IV. in the anterior mediastinum. This organ is not rarely found in the young adult. According to Rtidinger, its involution does not begin till the fifteenth year. The great fissure of the lungs begins on the left, a little above this section, and on the right just below it. The bifurcation of the trachea...