254 Leonard W. Williams 



part of the nucleus pulposus) "which often bears the irregular pro- 

 cesses, first described by Luschka, surrounds the notochordal remnants 

 (Reste) so that the two structures interlock with one another and a 

 sharply marked cavity, such as occurs in the child, does not exist." 

 The original article is in the Verh. phys. med. Gesellsch., Wiirzburg, 

 1859, IX, pp. 193-242. 



This clear and precise statement by so acknowledged a leader as 

 Ivoliiker did not suffice to settle the question, for in the following year 

 Eobin, describing carefully a large series of stages in the development 

 of the notochord of mammals, maintained that the notochord undergoes 

 mucoid degeneration and that its intervertebral expansion is gradually 

 invaded by papillae of fibro-cartilage which, meeting at its center and 

 expanding gradually, finally replace the degenerated notochordal tissue. 



Kolliker's theory of the origin of the nucleus pulposus was again 

 attacked in 1869. Dursy found that the nucleus pulposus is formed 

 primarily by the liquefaction of the connective tissue of the inter- 

 vertebral dis6 and that the notochord takes no part in the formation 

 of the definitive nucleus pulposus. This view is like Luschka's second 

 theory, except that he found that the notochord is liquefied first and 

 later fuses with the liquefied connective tissue. 



Ten years later Lowe entered the field in defense of Kolliker's theory. 

 He agreed essentially w^ith Kolliker, but found that the entire nucleus 

 pulposus of the adult rat is formed by the notochord. This difEerence 

 is merely one of definition, for, as was noted above, Kolliker considered 

 that the looser fibro-cartilage of the disc should be regarded as the 

 peripheral portion of the nucleus pulposus, which, by this definition, is 

 composed of the notochordal tissue and the loose fibro-cartilage of the 

 disc. 



Heiberg, 1878, says: "dann muss man zu dem Schluss kommen dass 

 die Chorda dorsalis beim Menschen keinen Antheil an der Bildung 

 der Pulpa des Intervertebralligamentes nimmt." 



In 1880 Leboucq published the last considerable article upon the ques- 

 tion of the fate of the mammalian notochord. He found that in the 

 human and in other mammalian embryos, the notochordal tissue is 

 practically destroyed long before birth. In the vertebra the notochord 

 degenerates and is absorbed, but the intervertebral notochordal expansion 

 is first invaded by connective tissue and is ultimately replaced by it. 



This piece of work, coming after a long controversy, was widely ac 

 cepted in spite of the fact that it contradicted practically all previous 



