. The American journal of anatomy . ouches to the dorsal side of the pharynx, and again are metby shorter growths from the dorsal aorta. Thus the third andfourth arches are formed and, as a glance at fig. 8 will show, theyalso, from their plexiform origin, are potentially multiple on eachside. With the growth of the pharynx the conus arteriosus, whichjoined the ventral aortae originally cephalad to the second arch,has moved caudad, and later opens almost directly into the thirdand fourth arches. This condition is represented in fig. 9. Herestill we see the plexus of the ventral aorta extending
. The American journal of anatomy . ouches to the dorsal side of the pharynx, and again are metby shorter growths from the dorsal aorta. Thus the third andfourth arches are formed and, as a glance at fig. 8 will show, theyalso, from their plexiform origin, are potentially multiple on eachside. With the growth of the pharynx the conus arteriosus, whichjoined the ventral aortae originally cephalad to the second arch,has moved caudad, and later opens almost directly into the thirdand fourth arches. This condition is represented in fig. 9. Herestill we see the plexus of the ventral aorta extending caudad fromthe ventral part of the fourth arch, as it did earlier from the sec-ond arch. Its plexus formation is easily recognized, as it liesin the thin sheet of mesoderm between the pharynx and the peri-cardial cavity, but it no longer crosses the median line on accountof the presence of the keel-like growth of the pulmonary anlagefrom the ventral wall of the pharynx. From the dorsal part of 124 JOHN LEWIS BREMER Ar. 2. 11: Fig. s Rabbit, LO days, 23 segments, , 940. Reconstruc-tion (if t he lil(Hid-vessels of 1 he head end of the embryo, seen from the ventral side ;t he heart removed by cutl ing through the conus arteriosus. Lettering same as infig. .), and also , , , aortic arches; , external carotid arte-ries, cut; x and //, remains of second channel for sec 1 aortic arch. X 125. the fourth arch and from the dorsal aorta sprouts arise, at firstin part solid, which curve around the pharynx and, entering thesame sheet of mesoderm in which the ventral aorta lies, form there, AORTA AND AORTIC ARCHES IN RABBITS 125 on the left side of the embryo, an anastomosing plexus. On theother side of this embryo these sprouts from the dorsal aorta aremuch simpler, though still double, while a lateral extension of theplexus of the ventral aorta replaces that derived, on the left, fromthe dorsal sprouts. In other embryos there is g
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectanatomy, bookyear1912
