VERTEBRAL LIGAMENTS 



227 



The anterior longitudinal ligament (figs. 259 and 265) commences as a narrow 

 band attached to the inferior surface of the occipital bone in the median line, 

 just in front of the atlanto-occipital ligament, of which it forms the thickened 

 central portion. Attached firmty to the tubercle of the atlas, it passes down as 

 the central portion of the atlanto-epistrophic ligament, in the mid-line, to the 

 front of the body of the epistropheus. It now begins to widen out as it descends,, 

 until it is nearly two inches (5 cm.) wide in the lumbar region. Below, it is fixed 

 to the upper segment of the sacrum, becoming lost in periosteum about the 

 middle of that bone; but is again distinguishable in front of the sacro-coccygeal 

 joint, as the anterior sacro-coccygeal hgament. 



Its structxire is bright, pearly-white, and gUstening. Its lateral borders are separated 

 from the lateral bands by clefts through which blood-vessels pass; they are frequently indistinct 

 and are best marked in the thoracic region. It is thickest in the thoracic region, and thicker in 

 the lumbar than the cervical. It is firmly conSecfed with the bodies of the vertebrae, and is 

 composed of longitudinal fibres, of which the superficial extend over several, while the deeper 

 pass over only two or three vertebrae. It is connected with the tendinous expansion of the pre- 

 vertebral muscles in the cervical, and the crura of the diaphragm are closely attached to it in 

 the lumbar region. 



Fig. 266. — Posterior Longitudinal Ligament. (Thoracic region.) 

 (Pedicles cut through, and posterior arches of vertebrae removed.) 



Lateral expanded portion' 



Median longitudinal band 



i 



The posterior longitudinal ligament (figs. 263, 266, 267, and 274) extends 

 from the occipital bone to the coccyx. It is wider above than below, and com- 

 mences by a broad attachment to the cranial surface of the basi-occipital. In the 

 cervical region it is of nearly uniform width, and extends completely across the 

 bodies of the vertebrae, upon which it rests quite flat. It does, however, extend 

 slightly further laterally on each side opposite the intervertebral discs. In the 

 thoracic and lumbar regions it is distinctly dentated, being broader over the inter- 

 vertebral substances and the edges of the bones than over the middle of the 

 bodies, where it is a narrow band stretched over the bones without resting on 

 them, the anterior internal vertebral venous plexus being interposed. The 

 narrow median portion consists of longitudinal fibres, some of which are super- 

 ficial and pass over several vertebrae; and others are deeper, and extend only from 

 one vertebra to the next but one below. 



The dentated or broader portions (fig. 267) are formed by obUque fibres which, springing 

 from the bodies near the intervertebral foramina, take a curved course downward and back- 



