NUMERICAL VARIATION IN THE HUMAN SPINE. 297 



It is clear, however, that the travelling of the thorax upward has not been symmet- 

 rical ; and that on the right (the side where it is less perfect) there is a small rib on the 

 lUth vertebra, which on the left is lumbar, and that moreover the change of the articular 

 processes occurs a verteljra lower on the right than on the left. This is another instance 

 of the tendency for each side to have twelve ribs somewhere. On the left, where there 

 is a good one in the neck, there is none on the 19th vertebra; on the right where that of 

 the 7th is rudimentary, so as practically not to be a rib at all, there is a small one on 

 the 19th. 



The arrangement of the lumbar, sacral and thoracic regions in this spine is far less 

 regular than in the preceding. It also, as far as the lower half of the spine is concerned, 

 is far more consistent with Rosenberg's theory. Not so the upper part. This on the left 

 is in some respects suggestive rather of the transformation of the 7th vertebra into a 

 thoracic than of a cervical rib. The arrangement of the cartilages of the 1st and 2d left 

 ribs is unique. On the other hand tlie shape of the rib from the 7tli vertebra is strik- 

 ingly like that of a cer\ica! ril) described by Gruber. 



INCOMPLETE SPECIMENS. 



Tlie following specimens are incomplete. All except 7737.-3, 8590, 132, 4767, and 

 1392 are, I believe, my additions to the Museum. While some of them are of little value, 

 others are rare, and some of them fit in very well to supplement the complete spines. 



Fusion of the Atlas axd Occiput. 



Five specimens, of which the last is probably pathological. 



7737.3. — An occipital bone and an atlas, evddently congenitally fused. The posterior 

 arch of the atlas is open behind. The left side of this arch is much less developed than 

 the other, and completely fused with the occiput except just behind the lateral mass 



the loss of a certain segment, .say the (ith, not only in the skeleton, but in the muscular and nervous systems. This is very 

 just; but why assume that a certain individual segment is wanting? Why not assume that between the occiput and the 

 segment whence comes the 1st thoracic vertebra there has from the very beginning been one segment less than usual, and 

 that the cour.se of development has been correspondingly modified ? Bolk's explanation is that the 1st segment, whence 

 comes the atlas, is by no means very stable, and that tlie division between the occiput and the cervical region has in this 

 spine occurred one segment too low. I have practically expressed in tliis paper my belief in the want of stability of the 1st 

 segment ; but what has become of it in ihis case '! We are not told that there are any traces of it in the occiput. Even if it 

 were found more or less incoi'porated with the occiput, it seems to me that it is expecting rather too much of the adaptive 

 powers of nature to have a perfect alla,s, :\.s in this case, come from the segment below the one normally producing it, after 

 the occurrence of an error in development. 



