File:Contributions to embryology (20696681371).jpg

Title: Contributions to embryology
Identifier: contributionstoe07carn (find matches)
Year: [1] (s)
Authors: Carnegie Institution of Washington
Subjects: Embryology
Publisher: Washington, D. C
Contributing Library: Gerstein - University of Toronto
Digitizing Sponsor: University of Toronto

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The figures on Plate I are designed to show diagrammatically the relations of the caudal end of the spinal cord and the vertebral column in a series of human embryos varying from 4 nun. to 67 mm. long, and are so arranged that the segmental levels, as indicated at the left, correspond throughout, the thirty-fourth segment being emphasised by a heavy line. In the two youiiger stages the segments were detennined by the myotomes; the remainder were determined b>- the sclerotomes, or the bodies of the vertebra. In making the diagram it was found necessary to make all the segments of the same width; in reality the more caudal ones are relatively much narrower. Also, the individual segments become wider in the older stages, whereas in the diagram they are kept at the same width. There is thus introduced an axial distortion which should be kept in mmd in studying the figures. In figures 1 to 15 the surface profile of the caudal region is indicated and the cloacal membrane la shown by a wider line. In figures 1 to 5 the caudal gut is shown by a broken line. In figures 4 and 5 it will be noted that a remnant of the gut is still present, though its communication with the cloaca is interrupted. Early stages in the foimation of the filum terminale are shown in figures 25 to 30. The figures in this plate are all based upon profile reconstructions made from the following embryos: Fig. Embryo. Fig. Embryo. Fig. Embryo. No. 836 11 No. 432 21 No. 75 810 12 837 22 145 371 13 431 23 221 14 453 24 449 389 15 382 2S 544 16 632 26 7 8S2 17 584a 390 18 406 28 406 19 1008 29 10 576 20 875 :)u 1656

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