253 Leonard W. Williams 



the siirrountling tissue, into the nucleus pulposus." (Bryce, in Quain's 

 Anatomy, Vol. I, Embryology, 1908, p. 49 and 252.) 



'"I'lie notochord not only remains intervertebrally, but gi'ows conlinu- 

 ously at that point, showing therewith the tendency (Neigung) after the 

 loss of its sheath, to fuse with the surrounding connective tissue. (Le- 

 boucq, 1880.) . . . The nucleus pulposus or gelatinosus of the inter- 

 vertebral ligament (intervertebral disc) consists in every case in the adult 

 manmial, of such common growth of the notochord and of the tissue 

 hdng next to it. G. Jager is indeed right when he compares, as men- 

 tioned above, the intervertebral longitudinal ligament (Liingsband) of 

 birds with the pnlpy nucleus of the disc of mammals." (Schauinsland, 

 in Hertwig's Handbuch d. vergl. u. exper. Entwickelungslehre der 

 Wirbeltiere, Bd. 3, Teil 2, 190G, 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 to- 

 gether the successive vertebrae (G. Jager, 1858)." 



"Finally the notochord disappears from the vertebral regions, al- 

 though 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-carti- 

 lages." (McMurrich, The Development of the Human Body, 1907, 

 p. 170.) 



"La corde dor sale, par exemple, constitue a elle seule tout le squel- 

 ette axial chex les Chordes primitifs, tandis qu'elle disparait entiere- 

 ment dans les formes superieures." (L. Vialleton, Un Probleme de 

 I'Evolution, 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 sub- 

 ject aroused considerable interest. Two theories were in the field: 

 one proposed in 1852 by Luschka, and advocated by Kolliker, H: 

 Miiller and Lowe; the other originated by Virchow, and defended by 

 Luschka after 1856, Eobin, 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 



