XITMERICAL VAIilATloX IN THE HUMAN SPINE. 



278 



Class IV. 



This class is coniposi'd of spines in wliicli tlicrc is a teiidencv to the ihniinution of tlie 

 nnnihcr of pracsacral vt'rtel)rae, wiiich teiKk'ncv. however, is not completely successful. In 

 everv casi' the 1^'ith vcrtehra is the f'ti/cf>i/ix. The spiiu's of tiiis class are divided into 

 four groups. 



Group A cousi.sts of two spines in which there is more or less fusion of two or more 

 vertebrae, which certainly occurred during- the course of development. Group B consists 

 of one spine in which the atlas is fused witli the occiput. Group (J also comprises but one 

 spine, in which tlu*re is a diminution of the cervical vertebrae to six, which loss is partially 

 compensated for hy an achlitioual lumbar saci-ali/ed on one side. In this latter respect the 

 spine belongs in the next group, but it is |)ut l)y itself on account of its gri'at rai'ity. 

 Group D consists of spines in which tiie last lumbar is more or less sacralized. 



The spines in Class IV are the following. Group A : 2r)4. Z: Group B: 24; Group C : 

 H-3; Group D: ;J4'.), 492, 257. A-2]!). A-7, 141. 



Groiqj A. 



Of the two spines in this class, tiu' first e\ddently has great peculiarities dependent on 

 a very early fusion of the elements of distinct vertebrae. In the second the process seems 

 more distinctly pathological, and belonging to a later period. 



264. Cat. ••M7;)-ol. 



Male, white, aet. 8S. C. 7. T. 12. L. o, S. o. C. 4. 



This spine, besides some exostoses and fusions, prob- 

 al)ly due to advancing age, has one remarkable mal- 

 formation in the cervical region. There is nothing worth 

 noting below tlie neck, unless it he that the 1st coccygeal 

 is fused with the sacrum and (hstinct from the otiier 

 coccygeals. The fusion, on one .side, of the lateral 

 nuxsses of the sacrum and the 1st coccygeal is complete. 



There are consideraljle irregularities of the nature 

 of exo.stoses on the front of the bodies of the last two 



264. 



