22 ANTHROPOLOGY. 



3. Special Anatomy of the Spine. 



A. Bones of the Trunk. 



The trunk is constituted by the vertebral column or spine, the thorax, 

 and the pelvis. 



The spine, columna veiiehralis, racliis {pi. 122, fig. S\ 4 '' '' \ fig. 5, A, B, c), 

 is placed at the posterior part of the trunk, and consists of twenty-eight or 

 twenty-nine pieces. Of these, twenty-four are called true vertebrae, and 

 connected by ligaments so as to form one strong but flexible column. The 

 twenty-fifth piece, reckoning from the head, is the sacrum, and is inserted 

 between the ossa innominata ; the remaining three or four constitute the 

 OS coccyx, and in their imperfect form represent the caudal vertebrge or tail 

 of other vertebrate animals. 



Each vertebra consists of a body, and of several projections or processes. 

 The body occupies the anterior central part ; it is thick and spongy, and 

 rather circular or oval ; its upper and lower surfaces are flat or slightly 

 concave, and give attachment to the inter-vertebral ligaments. The mar- 

 gin of each is tipped with a compact white substance, and the lower surface 

 is rather larger than the upper. Anteriorly it is transversely convex and 

 grooved horizontally, particularly on either side, and is likewise very 

 porous. Posteriorly it is concave, so as to form part of the spinal canal or 

 foramen. This surface is perforated by large foramina for the escape of the 

 venous canals which ramify through the bone. The processes of each ver- 

 tebra are nine, two lateral or the laminae, two transverse, four oblique or 

 articulating, and one spinous. 



The lateral processes^ or lamina?, arise one on each side, by a sort of pedicle, 

 I'rom the j^osterior part of the body ; they pass backwards, bounding the 

 sides of the spinal hole, and unite posteriorly in the spinous process ; they 

 are broad behind, but narrow where they join the body, being grooved out 

 above and below into a notch. The inferior of these is the larger. The 

 laminiB form the lateral and posterior portions of the spinal arch or foramen 

 for the spinal cord. The roots of these laminae, or the pedicles, are con- 

 sidered by some as separate portions ; they form the common point of 

 support for the other processes, and separate the superior from the inferior 

 notch. These notches, where the vertebree are joined, form the inter-ver- 

 tebral holes for the passage of the spinal nerves. 



The spinous process is the most projecting part of the vertebra in the 

 posterior median line ; its base is bifurcated, and passes into the two laminte ; 

 its apex generally ends in a point or tubercle. The whole series of these 

 processes presents the longitudinal prominent crest posteriorly, named spine. 

 Each process receives the insertion of tendons, and serves as a lever for the 

 extensor muscles of the column. 



The transverse processes arise from the roots of the laminae, or rather 

 from the pedicles, and are directed outwards on each side ; they serve for 

 the attachment of tendons, and in the dorsal region they also support the 

 ribs. 

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