The development of the human body; a manual of human embryology . arising from the ventral trunk near itsformer origin possibly representing the future lingualartery (His), and then the portion of the dorsal trunkwhich intervenes between the third and fourth branchialvessels vanishes, so that the dorsal trunk anterior to thethird branchial arch is cut off from its connection with thedorsal aorta and forms, together with the vessel of thethird arch, the internal carotid, while the ventral trunk,anterior to the point of origin of the third vessel, be-comes the external carotid, and the portion w
The development of the human body; a manual of human embryology . arising from the ventral trunk near itsformer origin possibly representing the future lingualartery (His), and then the portion of the dorsal trunkwhich intervenes between the third and fourth branchialvessels vanishes, so that the dorsal trunk anterior to thethird branchial arch is cut off from its connection with thedorsal aorta and forms, together with the vessel of thethird arch, the internal carotid, while the ventral trunk,anterior to the point of origin of the third vessel, be-comes the external carotid, and the portion which in- 264 THE DEVELOPMENT OF THE HUMAN BODY. tervenes between the third and fourth vessels becomesthe common carotid (Fig. 139). The rudimentary fifth vessel, like the first and second,disappears, but the fourth persists to form the aortic arch,there being at this stage of development two completeaortic arches. From the sixth vessel a branch ariseswhich passes backward to the lungs, and the portion ofthe vessel of the right side which intervenes between this. Fig. 138.—Arterial System of an Embryo op 10 mm. Ic, Internal carotid; P, pulmonary artery; Ve, vertebral artery; 777 to VI, persistent branchial vessels.—(His.) and the aortic arch disappears, while the correspondingportion of the left side persists until after birth, formingthe ductus arteriosus (ductus Botalli) (Fig. 139). Whenthe longitudinal division of the aortic bulb occurs, theseptum is so arranged as to place the sixth arch in commu-nication with the right ventricle and the remaining vesselsin connection with the left ventricle, the only direct com-munication between the systemic and pulmonary vessels / THE ARTERIES. 265 being by way of the ductus arteriosus, whose significancewill be explained later (p. 290). One other change is still necessary before the ves-sels acquire the ar-rangement which theypossess during fetallife, and this consistsin the disappearanceof the lower portionof the right aortic arch(F
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectembryol, bookyear1902
