////: v i-: it T VISUAL COLUMN. i; 



bones, though all eoiistnicted on an uniform typo, yet do not offer the sam- 

 configuration throughout the whole raehidean stalk. The differences they 

 present into this respect, have allowed of their being formed into five prin- 

 cipal groups; whence the division of the vertebral column in five regions, 

 which are, enumerating them from before to behind: 1, C> rriml i-ri/imt ; 

 -, Donal region ; 3, Luwbar region ; -t, Sacral region ; 5, Ooocygeal ri'ijin. 

 The first comprises ^ veil vertebra?, which servo as a base for the animal s 

 neck : the second has eighteen, against which the ribs are placed ; the third 

 has only six, which correspond to the loins ; in the fourth there arc five, 

 constantly solidified into one mass in the adult, to constitute a single b..ne 

 the Sdcniiii ; while the fifth possesses a variable number of small degenerate 

 vertebra-, gradually decreasing in size to form the tail. The pieces consti- 

 tuting the tirst three regions are called true vertebras ; those of the last two 

 are designated /f//.x/- vertebrae. 



The characters belonging to all these vertebne will be first studied ; then 

 a particular description of the vcrtebrao of each region will be given; and, 

 finally, an examination will be made of the spine as a whole. 



CHARACTERS COMMON TO ALL THE VERTEBRA. 



Ka-'h of these small bones is pierced from before to behind by a wide 



Fi>. 10. 



j -~i 



KII.MI.NTS OF A VERTKURA : AKTKK o\\|.\. 



A, Ideal typical vertebra; n, Actual thoracic vcrtrhr.i of a hinl ; --, Centrum (or 

 6x/y), giving off, d, </, the diapophyses, and y>, ;i. tin- puspnhyiM (tr.i,,*i-.-i-$c ud 

 s); the neural arch, iuclnsiu^ the spinal re ml, is formed by 

 n, n, the neuraj)j)hyses (Ad/iucr), and n, *, the neural spine (>/,/;,. /uv j,, 

 tin- h.-fiiial arch, inclosing the great centres of tho circulation, i> fnrineil l>y /i, /<, 

 tin- li:i-iua|.i'pliy-es (<:n*t'il i;irtil<i<ii's) ; and It, >, the ha'inal spine (*t,,i,>nn). 

 From In. th the iieurap'iphyses and (UHMfttphTMil may ) triveii ntl'thi- zy^a]Miphy-i-<, 

 z, z. The lateral arches, which may InaOM thi- vi-rti-iiral arteries, <, 

 roinpleteil l>y the pleu rapophy >e< ( /'iVv ),//.; t he-e ill l: are In-lit downwards, so 

 as to form part of the ha mal arch, and give off the diverging appendages, n, <i. 



opening, the spinal foramen ; whence results, for the entire spine, a long 

 canal traversing its whole length, and which lodges a very important 



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