Tufts College Studies; (Scientific Series).

Tufts College Studies; (Scientific Series).

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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1904 edition. Excerpt: ...the cord being continuous throughout. This connection between Meckel's cartilage and the extracolumella, like that between the extracoluniella and the hyoid arch, is 'My sections at this stage show no break in continuity between stapedial and extracolumella. rather to be compared with the connections which form in various ichthyopsida between the proximal ends of the branchial arches. As Gadow points out, it has nothing to do with the siphoneum. Gadow's suggestion that the system of cartilages and ligaments extending from the fenestra ovalis to the mandible is at least analogous with..... the hyomandibulosymplectic element of the fishes, hardly applies here, for the piscine_ chain of elements includes the quadrate as one constituent. In the crocodilia the quadrate is outside of this system. THE MIDDLE EAR OF THE PIG. In pig embryos 15.5mm. long no cartilage has as yet been formed, but procartilage is forming, and tracts of this stand out plainly in the stained section on account of the crowded condition of the nuclei (fig 7). In modelling this and similar early stages there is difliculty in saying just where procartilage leaves off and undifferentiated tissue begins, since these fade into each other and there is not that sharp differentiation which occurs later, when cartilage and perichondrium are formed. I have, however, modelled two embryos of this stage, one from transverse and the other from sagittal sections, and finding them to agree closely conclude that there is no serious error in them. At this stage there is not the slightest indication of an otic capsule, the membranous labyrinth being surrounded by undifferentiated mesenchyme, in which the nuclei are as scattered as at any other place. The tracts of...
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Product details

  • Paperback | 142 pages
  • 189 x 246 x 8mm | 268g
  • United States
  • English
  • black & white illustrations
  • 1236829298
  • 9781236829290