Henry Gray (18251861). Anatomy of the Human Body. 1918.
exists above its ventral portion (Fig. 468), but this foramen is ultimately closed by the fusion of the aortic septum with the ventricular septum.
FIG. 469 Diagrams to illustrate the transformation of the bulbus cordis. (Keith.) Ao. Truncus arteriosus. Au. Atrium. B. Bulbus cordis. RV. Right ventricle. LV. Left ventricle. P. Pulmonary artery. (See enlarged image)
When the heart assumes its S-shaped form the bulbus cordis lies ventral to and in front of the primitive ventricle. The adjacent walls of the bulbus cordis and ventricle approximate, fuse, and finally disappear, and the bulbus cordis now communicates freely with the right ventricle, while the junction of the bulbus with the truncus arteriosus is brought directly ventral to and applied to the atrial canal. By the upgrowth of the ventricular septum the bulbus cordis is in great measure separated from the left ventricle, but remains an integral part of the right ventricle, of which it forms the infundibulum (Fig. 469).
FIG. 470 Diagrams to show the development of the septum of the aortic bulb and of the ventricles. (Born.) (See enlarged image)
FIG. 471 Transverse sections through the aortic bulb to show the growth of the aortic septum. The lowest section is on the left, the highest on the right of the figure. (After His.) (See enlarged image)