Embryology - 19 Apr 2024 Expand to Translate
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Williams, LW. The Later Development of the Notochord in Mammals. (1908) 8:251-284.

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The Later Development of the Notochord in Mammals

By

Leonard W. Williams.

From the Laboratory of Comparative Anatomy, Harvard Medical School.

The fate of the notochord in mammals has received, in recent years, very scant attention. This is well exemplified both by the briefness of the discussions of the subject in recent text—books and also in reference works, and by the contradictory statements found in different, or even in a single book.

The following shades of opinion are found in volumes which have appeared very recently:

“The notochord here” (in mammals) “persists longer intervertebrally than intravertebrally, but it disappears entirely by the time the adult condition is reached.” (_Wiedersheim’s Comparative Anatomy, 6th lrerman edition, 1906, p. 62, and 3d English edition, 1907, p. 60.)

“They (the intervertebral discs) are developed, like the bodies around the notochord, persisting parts of this structure forming a central core to each. disc.” (Pierso1’s Anatomy, 1907’, p. 132.)

“The notochordal remains lying between each pair of vertebrae with the perichordal tissue grow and remain throughout life as the nuclei pulposi of the intervertebral discs.” (Bcnnet, Entwicklungsgeschichto, 1907, p._ 381.)

“The notochord is essentially an embryonic structure in mammals, although it does not completely disappear, for traces of it are to be found throughout life in the middle of the intervertebral discs. When fully developed it is a cylindrical rod composed of clear epithelium-like cells, enclosed within a special sheath of homogeneous substance. These cells, although they may become considerably enlarged and vacuolated, undergo no marked histogenetic change and take no part in the formation of any tissue of the adult. . . . Within the (intervertebral) disc the notochord is enlarged and afterwards converted in each, along with the surrounding tissue, into the nucleus pulposus.” (Bryce, in Quain’s Anatomy, Vol. I, Embryology, 1908, p. 49 and 252.)

“The notochord not only remains intervertebrally, but grows cont inuously at that point, showing therewith the tendency (Neigung) after the loss of its sheath, to fuse with the surrounding connective tissue. (Leboucq, 1880.) . . . The nucleus pulposus or gelatinosus of the intervertebral ligament (intervertebral disc) consists in every case in the adult mammal, of such common growth of the notochord and of the tissue lying next to it. G. Jéiger is indeed right when he compares, as mentioned ahove, the intervertebral longitudinal ligament (Langsband) of birds with the pulpy nucleus of the disc of mammals.” (Schauinsland, in Hertwig’s Handbuch d. vergl. u. exper. Entwickelungslehre der Wirbeltiere, Bd. 3, Teil 2, 1906, p.. 517.) The statement referred to is as follows: “Only inconspicuous remnants of it remain finally in the interior of the intervertebral ligament; they lie there enclosed in a longitudinal band which, as the ‘ligamentum suspensorium,’ binds together the successive vertebrae Jager, 1858).”

“finally the notochord disappears from the vertebral regions, although a canal, representing its former position, traverses each body for a considerable time, and in the intervertebral regions it persists as relatively large ﬂat discs, forming the pulpy nuclei of the fibro—cartilages.” (McMurrich, The Development of the Human Body, 1907, p. 170.)

“La corde dorsale, par exemple, constitue a elle seule tout le squelette axial chex les Chordés primitifs, tandis qu’elle disparait entiercment dans les formes superieures.” (L. Vialleton, Un Probleme de l’Evo1ution, 1908, p. 87.)

The cause of this unﬂattering state of our knowledge is that the theory concerning the fate of the notochord of mammals, which was widely accepted years ago, was not well founded and does not explain the known facts. In the three decades between 1850 and 1880 the subject aroused considerable interest. Two theories were in the field: one proposed in 1852 by Luschka, and advocated by Kolliker, I-In Muller and Ldweg the other originated by Virchow, and defended by Luschka after 1856, Robin, Dursy, and Leboucq.

The nucleus pulposus in man was carefully described, in 1852, in the first edition of “Die Halbgelenke,” by Luschka, who found that it arises from the intervertebral expansion of the notochord.

Virchow later contended that the nucleus pulposus of the new-born

Cite this page: Hill, M.A. (2024, April 19) Embryology Paper - The Later Development of the Notochord in Mammals. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Paper_-_The_Later_Development_of_the_Notochord_in_Mammals

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