File:Outlines of comparative physiology touching the structure and development of the races of animals, living and extinct - for the use of schools and colleges (1870) (14596131550).jpg

Identifier: outlinesofcompar00agas (find matches)
Title: Outlines of comparative physiology touching the structure and development of the races of animals, living and extinct : for the use of schools and colleges
Year: 1870 (1870s)
Authors: Agassiz, Louis, 1807-1873 Gould, Augustus A. (Augustus Addison), 1805-1866 Wright, Thomas, 1809-1884
Subjects: Physiology, Comparative Zoology
Publisher: London : Bell & Daldy
Contributing Library: MBLWHOI Library
Digitizing Sponsor: MBLWHOI Library

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jaw. the branchial arches; The line ^1th the asterisk indicates the the extremities show natural length of the embryo,themselves upon the ex-ternal aspects of the same laminae. Of the extremities there isstill no trace to be discovered in the first half of the third day(fig. 339), but in the second half of that day they arise onthe sides of the ventral laminae as narrow edgings, which bythe close of the day have turned more upwards, gained theouter margins of the ventral laminae, and changed intorounded offsets (fig. 341, o, p\ the posterior pair being dis-tinguished from the anterior by somewhat greater breadth(fig. 345, o, p) ; on the fifth day they recede still more up- 318 EMBRYOLOGY. wards towards the dorsal laminae, become pediculated, andpresent a broad shovel-shaped termination (fig. 344, f, g). (§ 490. The vascular lamina in its development follows thephases of the first, or vitellicular circulation, which, as hasbeen stated, attains its height on the fourth day (fig. 346).
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Fig. 346.—View of the vitellus, magnified rather more than two diame-ters, exhibiting the circulation of the blastoderma completely developed:—a, Vitellus ; b, vena s. sinus terminalis; ft2, point of approximation to theembryo of the terminal sinus, and its communication with the veins, g, g ;c, aorta; d, punctum saliens, or pulsating point of the heart; /, /, arte-ries of the blastoderma; g, g, veins of the same (one inferior, two supe-rior ; sometimes there is but one above as well as below); e, e, the fiddleor guitar-shaped area pellucida; h, the eye. (This figure will be found tocorrespond in almost every particular with that of Pander, tab. iv. fig. 1,of his well known work, Entwickelungsgeschichte des Huhnchens im Eie).The more delicate ramifications of the vessels and their numerous inos-culations with the bounding sinus are omitted. DEVELOPMENT OF THE CHICK SECOND PEEIOD. 319 Immediately under the head of the embryo, three blood-redbounding points are seen (fig. 346, d), t

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