Outlines of comparative physiology touching the structure and development of the races of animals, living and extinct : for the use of schools and colleges . atulous towards the vitellus ; from whichundoubtedly it derives formative materials. x2 308 .EMBRYOLOGY. SEC01SD PEEIOD OF THE DEVELOPMENT OF THE CHICK, TOTHE EVOLUTION OF THE SECOND CIECULATION. [§ 487. THE second period in the history of the developmentof the chick begins with the third day, in the course of whichthe circulation in the vitelline vessels is completely established(figs. 339 and 346), and embraces farther the changes thatt
Outlines of comparative physiology touching the structure and development of the races of animals, living and extinct : for the use of schools and colleges . atulous towards the vitellus ; from whichundoubtedly it derives formative materials. x2 308 .EMBRYOLOGY. SEC01SD PEEIOD OF THE DEVELOPMENT OF THE CHICK, TOTHE EVOLUTION OF THE SECOND CIECULATION. [§ 487. THE second period in the history of the developmentof the chick begins with the third day, in the course of whichthe circulation in the vitelline vessels is completely established(figs. 339 and 346), and embraces farther the changes thattake place during the fourth and fifth days, till the allantoishas appeared, the membrane of the shell has been attained,and the second circulation is established ; the first, which hadreached its highest development at the end of the fourth day,now beginning to suffer an arrest, and to decline in extent andactivity (figs. 341 and 345). In the course of this period theembryo is completely detached from the germinal membrane,and becomes enveloped in peripheral productions of the samepart. The third day is the most remarkable in the whole f rt 7) .7 I a. Fig. 338.—Ideal section of an embryo somewhat younger than that offig. 339. A, transverse section ; a, vitelline membrane ; b,b, laminae dorsaleset vertebrales; b-, b~, laminae abdominales and transverse processes; c,c,lamina mucosa, which is seen bending round under the chorda dorsalis (e),to form the intestinal canal; d, d, lamina vasculosa; /, /, peripheral por-tion of the lamina serosa, proceeding to form the lateral involucra and theamnion ; g, medulla spinalis.—B, longitudinal section; a, vitellary mem-brane ; b, lamina serosa, and dorsum of the embryo ; b~, head of theembryo ; c, c, lamina mucosa ; d, lamina vasculosa; d2, heart; d3, branchialarteries ; c?4, aorta ; d5, artery of the blastoderma (arteria vitellina). DEVELOPMENT OF THE CHICK SECOND PEEIOD. 309 history of the development, as, from the general vigour of t
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectzoology, bookyear1870
