. The development of the chick : an introduction to embryology. Embryology; Chickens -- Embryos. 156 THE DEVELOPMENT OF THE CHICK ment of the nuclei leaves thin non-nucleated strips (septa) be- tween adjacent neuromeres. The interneuromeric projections are most pronounced laterally and fade out dorsally and ventrally. Behind the neuromeric portion of the hind-brain is a portion extending to the posterior end of the fourth mesoblastic somite from which the twelfth cranial nerve arises. The Neural Crest and the Cranial and Spinal Ganglia. The cranial and spinal ganglia owe their origin to a stru
. The development of the chick : an introduction to embryology. Embryology; Chickens -- Embryos. 156 THE DEVELOPMENT OF THE CHICK ment of the nuclei leaves thin non-nucleated strips (septa) be- tween adjacent neuromeres. The interneuromeric projections are most pronounced laterally and fade out dorsally and ventrally. Behind the neuromeric portion of the hind-brain is a portion extending to the posterior end of the fourth mesoblastic somite from which the twelfth cranial nerve arises. The Neural Crest and the Cranial and Spinal Ganglia. The cranial and spinal ganglia owe their origin to a structure known as the neural crest, which is a practically continuous cord of cells, lying on each side in the angle between the neural tube and the ectoderm, extending from the extreme anterior to the pos- terior end. Like other meristic structures the anterior portion. ^// ^y^.A^s. ^^ ^^ ^^ ^^ Fig. 89. — Frontal section of the hind-brain region of an embryo of about 36 s. Ot., Otocyst. N. 6, N. 7, N. 8, N. 9, N. 10, N. 11, Neuromeres, 6 to 11, according to Hill's enumeration, s. 1, s. 2, s. 3, First, Second, and third somites. V, Primordium of the trigeminus. VII-VIII, Primordium of the acustico-facialis. of the neural crest is the first to arise (at about 6-7 s stage), and the remainder appears in successive order during or shortly after the closure of the neural tube in each region; thus it is not until after the completion of the neural tube that the last portion of the neural crest is established. But before this time successive enlargements of the cranial part of the crest have formed the primordia of the cerebral gan- glia, and similar successively arising enlargements of the parts of the crest opposite the mesoblastic somites form the rudiments of the spinal ganglia. The intervening portions of the crest form the so-called interganglionic commissures, which subsequently. Please note that these images are extracted from scanned page images that may have been digitally en
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Keywords: ., bookauthorlilliefrankrat, bookcentury1900, booksubjectembryology
