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head joint ; having for artificial ground the lower 

 jaw, and, in a measure the shoulder sockets. 



For the hicomposite spine, at the head joint ; hav- 

 ing for a ground the terminations of the posterior 

 and anterior hmbs, and for an artificial ground the 

 eyeballs. 



The composite spine, in forming with the an- 

 terior Hues, acts first with the lower C of the neck, 

 and therefore on the upper end of the sternum as 

 an artificial ground ; in forming with the posterior 

 Unes it acts first with the upper C of the third S, 

 and therefore on the lower end of the sternum in 

 that relation. 



All combine, more or less, on the eyeballs, and 

 finally the bicomposite spine joins its action -with 

 that of the ophidian and these points. 



Eighth. — As has been before noticed, the pressure 

 of each point of application principally produces 

 the concave under it (§21 and following). Thus 

 the anterior (left) concave is mainly due to the 

 pressure of the left anterior point of appHcation, and 

 the effect of its line if carried throughout the S 

 would be to make it wholly concave to the left. 



In the same way, the right posterior pressure 

 extended would form the whole line concave to the 

 right. 



9 



