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the transverse process of the second vertebra, but a small one appears 

 on that of the 3rd vertebra {T. 5, Fig. 5), whilst on the transverse 

 processes of the fourth and fifth vertebrae large epiphyses of peculiar 

 form appear (T. 4, T. 5, Fig. 5). In the specimen from which Figure 5 

 was drawn all these 

 centres could be seen as 

 represented on the right 

 side, whilst on the left 

 side ossification was some- 

 what more advanced. 



Fig. 5. The Sacrum from 

 behind. On the rtght side all 

 the components of the Auricular 

 facet and the tuberosity are 

 separate. On the left side T. 5 

 and A. C. 4 have joined together. 

 No epiphysis is visible on the 

 site of the transverse process 

 of the second sacral vertebra. 



Subsequent process of ossification : 



1) The formation of the auricular facets. 



So far as my specimens shew, the auricular facets are in the 

 main formed from the costal epiphyses. Each pair extending upwards 

 mainly, but also somewhat downwards, and fusing together ultimately 

 to form one plate. 



In those cases in which the fifth lumbar vertebra fuses with the 

 sacrum the upper part of the auricular facet is certainly derived in 

 part from downward extension of the epiphysis of the transverse process 

 of the 1st sacral vertebra, as seen in Fig. 2, T 1. 



2) The formation of the tuberosities. (By tuberosity one under- 

 stands that part of the lateral border of the sacrum which lies below 

 the level of the auricular facet.) 



The manner of their formation appears to be the following. First 

 the epiphysis of the transverse process of the fifth lumbar vertebra 

 fuses with the costal epiphysis of the fourth sacral vertebra, as seen 

 in Fig. 5, left side. Next, the epiphysis of the transverse process of 

 the fourth vertebra elongates in the downward direction forming a 

 comma-shaped mass which comes into contact and fuses with the epi- 

 physis of the transverse process of the fifth vertebra and finally from 

 the point of fusion of these two, there grows upwards an extension 

 of bone which in course of time meets and fuses with the costal epi- 

 physis of the fourth sacral vertebra. This upward extension can be 



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