ii 



SKKI.KTO*. 



firtt two, they are U connrcU-d by interposed duct of a Tory elastic 

 substance, the iutervertebral cartilage!. 



Fir- . 



The general characters of the Vertebra; may be best studied on one 

 from the lumbar region ; in which the following parts, common to 

 nearly all of the 24, are well marked : a body, a ring, a spinous pro- 

 can, two transverse processes, four articulating processes, and four 

 notches. In the annexed plate two lumbar vertebra are represented : 

 that in the figure A, as seen obliquely from behind, from above, and 

 from the right side ; and that in the figure B, as seen from above and 

 behind. 



Fig. 3. 



1 



The Body (1) is a disc of bone with a nearly oval outline, larger 

 above and below than ut iU mi. Ml-, and having its greatest dimension 

 from side to nido. It< texture i* spongy, invested with a thin layer 

 of compact tiuc. It* upper and lower surfaces, by which it is 

 affixed to the two adjacent intervertebral cartilage*, are nearly flat, 

 and slightly markc.l by radiating lines. At its posterior border the 

 oval outline is interrupted by a slight concavity (2), which formi a 

 portion of the ring surrounding the spinal marrow, and in which 

 there are several apertures larger than those on the rest of the body, 

 for the exit of the veins from the interior. 



To either side of the posterior part of the body, and near its upper 

 border, is affixed one of the extremities of the arch (3) by which the 



ring is completed behind. It is composed of two flat lamina, which 

 spring from the side* of the body, and meet at an obtuse rounded 

 angle in the middle line behind, where they bear the spinoui process 

 (5). The space (4) included between the body and these lamina; is 

 called the vertebral foramen ; it is occupied l.y the spinnl cord ; it is 

 of a somewhat triangular form, and in the lumbar vertebra is of large 

 :.. 



Close to the attachments of the lamina; to the body there is in each 

 of their borders a rounded notch (6) ; and when the vertebra) are 

 applied one on another, these notches form oval holes (the intervcrte- 

 bral foramina, see next figure (S), through which the spinal nerves 

 pass, one pair going out between each two vertebra;. [NEnvoua 

 SYSTEM.] To the rest of the lamina; are attached the intorlaminar 

 ligaments, or ligamenta subfiava, bands of very elastic tissue by which 

 the spaces between the adjacent arches are filled up, and the spinal 

 canal completed behind, as it is by the intrvertebral cartilages before. 



The Spinous Process (5) is a broad flat quadrilateral portion of bone 

 directed horizontally backwards from the meeting of the lamiiiic. Its 

 posterior border is thickened, and to it, as well as to the upper and 

 lower borders, are attached strong ligaments binding the spinous pro- 

 cess of each vertebra to those next above and below it. The trans- 

 verse processes (7) project horizontally outwards on cither side ; they 

 are thin and long, and are enlarged and rough at their ends, to which 

 several strong muscles and ligaments are attached. The artii-nlutiiu; 

 processes are flat and oral ; each has a smooth surface, by which it U 

 connected with the corresponding part of the next vertebra above or 

 below. The upper pair (8) are set most widely apart, and their articu- 

 lating surfaces are concave and turned inwards ; the lower pair (9) 

 are nearer together, and have their articulating surfaces turned out- 

 wards. When the lumbar vertebra; are put together, the lower pro- 

 cesses of each are locked within the upper processes of the one next 

 below, so that scarcely any lateral or rotatory motion is in this part 

 of the spine possible. 



The Dorsal Vertebra, which in the adjacent plate are drawn, as 

 seen in A and B, from behind and from the left tide, and in C from 



Fig. 4. 



1.... 



before and from .the same side, have the same general characters as 

 the lumbar, but are distinguished from them by the following : 



The body (1) is small but deep, and longer from before backwards 

 than in any other direction ; its general outline in heart-shaped ; it has 

 at each border, just in front of the attachment of the lamina;, a 

 shallow depression (2) ; and when the vertebra) are set together, the 

 depressions on either side of each adjacent pair form one cavity, into 

 which the head of one of the ribs (G 3) is received for articulation. 

 The lamina; are bro.id and thick ; the vertebral foramen is oval and 

 small. The spinous process (5) is long and narrow, and projects 

 obliquely downwards ; those of adjacent vertebra) are imbricated at 

 their bases (fig. B). The transverse processes (6) ore long and directed 

 backwards as well as outwards ; each of them (except those of the 

 two last vertebra;) has a smooth surface in front of its outer extremity, 

 l.y which it articulates with the tubercle of the corresponding rib. 

 The articulating processes (7), both superior and inferior, arc equally 

 wide apart ; the former have their smooth surfaces turned backwards, 

 tho latter theirs forwards. The notches and foramina are smaller 

 in in in the lumbar vertebra;. 



The Cervical Vertebra;, of which one is represented in the following 

 cut, as seen from behind and above, are distinguished by the body (2) 

 being small, broad, and shallow, and wider above than below. In its 



