Development of the Notochord 255 



writers, for it indicated that the notochord disappears much earlier than 

 had been believed by others. 



Fric, however, in his "Handbuch der Gelenke" (1904), accepts Kolli- 

 ker's work and, figuring the nucleus pulposus, describes its peculiar tissue 

 as the remnant (Eest) of the notochord. 



Turning now to Miiller's contention that Virchow's tumor, Ecclion- 

 drosis physalifora, actually arises from the notochord, not from cartilage, 

 we find Virchow's view universally accepted until 1894, when H. 

 Steiner, working under Eibbert, published a careful study of a case 

 of the tumor and found that Miiller was right in believing it to be an 

 abnormal growth of the notochord. 



Eibbert, a year later, proved that the tumor can be produced ex- 

 perimentally in the rabbit, by puncturing the intervertebral ligament 

 so as to allow a portion of the nucleus pulposus to escape. This tissue, 

 lying in the connective tissue and muscle near the ligament, grows for 

 some time and forms a characteristic Ecchondrosis pliysalifora. This 

 knowledge led Eibbert in his "Geschwiilstlehre," 1904, to propose and use 

 the name chordoma, instead of Virchow^s name for the tumor. Fischer 

 and Steiner, working in Eibbert's laboratory, described a case of malign 

 chordoma in 1906. 



The generally accepted interpretation of the formation of the ver- 

 tebrae in the Amniota is the theory of Eemak of the resegmentation 

 of the vertebrae. Among recent exponents of Eemak's attractive gen- 

 eralization are Schultze, Schauinsland, Weiss, and Bardeen. Accord- 

 ing to this theory the vertebrae are formed by the division of the sclero- 

 tomes and by the subsequent fusion of the sclerotome halves adjacent 

 to each intersegmental plane to form an intersegmental vertebra. The 

 fissure of von Ebner, or the intervertebral fissure, a mid-segmental 

 transverse diverticulum of the myocoele which in mammals, however, 

 arises independently of the myocoele and after its disappearance, divides 

 the sclerotome into half segments. The anterior half of each sclero- 

 tome is formed of looser tissue than the posterior half. The latter is 

 apparently a mesenchymal condensation and has been called "the primi- 

 tive vertebra" by Eemak, the "scleromere" by Bardeen. Its central 

 portion is the "hypochordal rod" of Froriep, the "horizontal plate" of 

 Weiss, and the "primitive disc" of Bardeen. Its lateral portions are the 

 "vertebral arches" of Froriep, and the "costal and neural processes" 

 of Bardeen. Weiss divides the lateral portion of the primitive ver- 

 tebra into a "vertical plate" which extends backward from the outer 



