. The development of the chick; an introduction to embryology . ave been established; indeed, therhythmical pulsation begins at about the stage of 10 somiteswhen the neural crest is yet undifferentiated, and no neuroblastsare to be found anywhere. Either, then, the heart-beat is of mus-cular origin (myogenic), or, if of nervous origin, the nerve-cellsconcerned must exist in the wall of the cardiac tube ah initio. The first trace of nerve-cells is found in the heart of the chickabout the sixth day. These cells are at the distal ends of branchesof the vagus, with which they have grown into the h
. The development of the chick; an introduction to embryology . ave been established; indeed, therhythmical pulsation begins at about the stage of 10 somiteswhen the neural crest is yet undifferentiated, and no neuroblastsare to be found anywhere. Either, then, the heart-beat is of mus-cular origin (myogenic), or, if of nervous origin, the nerve-cellsconcerned must exist in the wall of the cardiac tube ah initio. The first trace of nerve-cells is found in the heart of the chickabout the sixth day. These cells are at the distal ends of branchesof the vagus, with which they have grown into the heart. Pre-vious to this time these neuroblasts are found nearer to the vagusalong the course of the arteries. There can be but little doubtthat they have arisen from the vagus ganglion and that theyreach the heart by migration. Such an origin has been demon-strated with great probability for all the known nervous elementsof the heart of the chick. (See Wilhelm His, Jr., Die Entwickelungdes Herznervensystems bei Wirbelthieren.) 260 THE DEVELOPMENT OF THE CHICK.
Size: 1978px × 1263px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorlilliefrankrattray187, bookcentury1900, bookdecade1910
