342 



in this series which have been sufficiently described. Is this con- 

 dition a return to the past (if so, to what past?), or a step towards 

 the future? 



The Fusion of the Axis and 3d Vertebra. There are 

 certain places where fusion exceptionally occurs in the course of de- 

 velopment, as between atlas and occiput, last lumbar and 1st sacral, 

 last sacral and 1st coccygeal. There is another place which seems 

 one of predilection, namely between the axis and the vertebra below 

 it. Leboucq has described two cases, both with imperfect ribs on 

 the 8th vertebra, in which he thinks there is a partial reduplication 

 of the axis, inasmuch as in certain fissures on the anterior surface 

 he sees a repetition of the superior articular surfaces of the axis 

 placed ventrally to the intervertebral foramina. This is the case only 

 in his first specimen. In the second the fusion is more thorough, and 

 the lines of separation lost. In the latter, moreover, there is an in- 

 timate fusion of the arches. I am somewhat inclined to question the 

 accuracy of the interpretation because these fissures on the anterior 

 surface, judging from Leboucq's drawing, do not correspond with the 

 direction of the superior articular surfaces of the atlas. These latter 

 slant from the middle downward and outward, while the fissures are 

 iDclined upward and outward. Moreover, in the first of my detached 

 specimens there is on the right of the anterior surface a horizontal 

 slit below the superior articular process of the atlas that looks at 

 first like a repetition of it, but which, as is shown by the median 

 section, is certainly in the axis and not between them. Neither in 

 Leboucq's second case nor in any of my series is there another in- 

 stance in such an appearance. In this series there are two cases of 

 fusion of these vertebrae without any history of the rest of the 

 column. In the complete spines there are two other cases, one certain 

 and one perhaps somewhat doubtful. The former (264) has the bodies 

 fused and the laminae on one side so intimately mixed as to appear 

 as one. In 297 (26 praesacrals) the bodies are fused but apparently 

 not mixed (if I may use the expression), but there is a fusion in the 

 arch that points to a congenital condition. Leboucq thinks there is 

 no doubt that there is an intercalation of the 3d vertebra, which, at 

 least in one case, he considers a partial reduplication of the atlas. 

 In neither of my cases is there any reason to see more than fusion. 

 Leboucq asks whether we are to consider his finding twice an inter- 

 calated vertebra at this place anything more than a simple coincidence. 

 He thinks that the place below the axis is a critical one in the cer- 

 vical column, and that the 3d vertebra is exposed to more variations 



