Development of the Notochord 279 



masses of tissue imbedded in the retropharyngeal connective tissue which 

 are very similar both to the adult notochordal tissue pictured by Kolli- 

 ker and Fric and to the tissue of chordoma. The posterior part of the 

 notochord is forced upward and backward and forms a large mass upon 

 the upper surface of the skull-base a short distance in front of the tip 

 of the tooth of the axis. The anterior part of the notochord is forced 

 forward and, forming a large mass between the cartilage and the 

 perichondrium of the hypophysial fossa, persists longer than elsewhere 

 in the skull. "We have seen that notochordal tissue, which is enclosed 

 in a large mass of cartilage, is either forced from the cartilage or is 

 enclosed in it and degenerates. If the tissue escapes from the cartilage 

 it undergoes a typical cytomorphosis and forms adult notochordal tis- 

 sue which is in all essentials like chordomal tissue. If this same 

 process takes place in the skull we should expect to find notochordal 

 tissue forced by the first chondrification of this region, that of the 

 dorsum seller., either forward into the hypophj^sial fossa, or backward 

 and upward upon the dorsum sellce. The chondrification of the pos- 

 terior end of the parachordal plate would, under the same conditions, 

 force the notochord backward toward the apex of the odontoid process 

 of the axis, or forward. In the latter case the notochordal tissue would 

 be forced either out under the skull or forward to the junction of the 

 sphenoidal and occipital cartilages or bones. Chordoma occurs at all 

 these points, except between the pharyngeal epithelium and the skull, 

 and only at these points. It occurs most frequently upon the dorsum 

 sellce, less frequently in the hypophysial fossa and at the spheno-occipi- 

 tal junction, and in the maligiiant case reported by Fischer and Steiner 

 it was found upon the upper surface of the basi-occipital bone. It should 

 be noted also that the tumors which occur at the spheno-occipital junc- 

 tion lie in the marrow spaces, as though the tissue of the tumor had 

 been forced into the bone under great pressure, as would be the case if 

 notochordal tissue were compressed by the growth of both bones. 



It seems to me probable that at least the majority of chordomas are 

 comparable to cranial nuclei pulfosi, and that chordoma should not be 

 regarded as an abnormal growth of notochordal tissue, but merely a 

 normal growth in an abnormal position. I am confident that chor- 

 doma also occurs beneath as well as above the spheno-occipital junction, 

 but no such cases have been reported. 



