. The development of the chick; an introduction to embryology. Birds -- Embryology. LATER DEVELOPMENT OF VASCULAR SYSTEM 349 left one first at an early stage and the right one later. The left auricle is thus larger than the right for a considerable period of time in the early development. When the right auricle grows out it passes above the bulbus, which is already in process of rotation, and the two auricles then expand ventrally on each side of the bulbus. The apex of the ventricle belongs primarily to the left side and this remains obvious as long as the external interventricular groove exi
. The development of the chick; an introduction to embryology. Birds -- Embryology. LATER DEVELOPMENT OF VASCULAR SYSTEM 349 left one first at an early stage and the right one later. The left auricle is thus larger than the right for a considerable period of time in the early development. When the right auricle grows out it passes above the bulbus, which is already in process of rotation, and the two auricles then expand ventrally on each side of the bulbus. The apex of the ventricle belongs primarily to the left side and this remains obvious as long as the external interventricular groove exists. In the adult the apex of the heart belongs to the left Fig. 199. — Ventral view of the heart of a chick embryo of 5 mm. head-length. (After Masius.) Atr. d., s., Right and left auricles. B. Co. Bulbus cordis. V. Ventricle. The varying positions occupied by the chambers of the heart in rela- tion to the body axes constitute a serious difficulty in describing the development. For instance, the auricular canal is at first in front of the atrium (before any bending of the heart takes place). As the ven- tricular loop turns backward and beneath the atrium, the auricular canal is ventral to the atrium; and finally, as the ventricles assume their definitive position behind the auricles, the derivatives of the auricular canal (auriculo-ventricular openings) come to lie behind the atrium. In other words, the atrium rotates around a transverse axis through nearly 180 degrees in such a way that its original anterior end becomes succes-. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Lillie, Frank Rattray, 1870-1947. New York, Holt
Size: 1440px × 1735px
Photo credit: © Paul Fearn / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorlilliefrankrattray187, bookcentury1900, bookdecade1900
