204 COMPARATIVE ARTHROLOGY 



There are no intertransverse joints in the lumbar region. 



Pig. — The hgamentum nuchae is represented by a fibrous raph^ and thin 

 layers of elastic tissue which extend between the cervical spines. 



The atlanto-occipital and atlanto-axial joints resemble those of the dog. 



The interspinous ligaments of the neck are elastic. 



Dog. — The ligamentum nuchse consists of a small fibrous band which extends 

 from the spine of the axis to the anterior thoracic spines; it may be regarded as a 

 mere fibrous raphe between the right and left muscles. 



There are interspinous muscles instead of ligaments in the neck. 



There are three ligaments in connection with the odontoid process. The two 

 alar ligaments (Ligamenta alaria) arise on either side of the odontoid process, 

 diverge, and end on either side of the foramen magnum. The transverse ligament 

 of the atlas (Ligamentum transversum atlantis) stretches across the dorsal surface 

 of the odontoid process and binds it down on the ventral arch of the atlas, a bursa 

 being interposed. It is attached on either side to the lateral masses of the atlas. 



The two capsules of the atlanto-occipital joint communicate with each other, 

 and usually with the capsule of the atlanto-axial joint also. 



Articulations of the Thorax 



Ox. — The second to the eleventh costo-chondral joints inclusive are diarthroses 

 with close capsules, reinforced externally. (They are synchondroses in the sheep.) 

 The upper parts of the cartilages are attached to each other by distinct elastic 

 ligaments (Ligamenta intercostalia). 



The first pair of chondro-sternal joints are separate from each other; inter- 

 crossing fibers unite the costo-chondral junctions above the joints. 



The first segment of the sternum forms a diarthrosis with the body. The 

 anterior joint surface is concave, the posterior convex. The joint (Articulatio 

 intersternalis) is surrounded by a close capsule, and the joint surfaces are attached 

 to each by a small intra-articular ligament. Limited lateral movement is possible. 

 (In the sheep the joint is a synchondrosis.) 



Both surfaces of the sternum are covered by a layer of fibrous tissue. 



Pig. — The second to the fifth or sixth costo-chontlral joints are diarthroses. 

 The intersternal articulation and the sternal ligaments resemble those of the ox. 



Dog. — The first chondro-sternal joints do not coalesce. 



The internal sternal ligament divides into three bands. 



TEMPORO-MANDIBULAR ARTICULATION 

 Ox. — The articular surfaces are of such a character as to permit more extensive 

 lateral movement than in the horse. 



The condyle of the mandil)le is relatively small and is concave transversely. The temporal 

 articular surface is extensive and is convex in both directions. The postglenoid process is small. 



Pig. — The considerable longitudinal diameter of the temporal articular sur- 

 faces and the very small size of the postglenoid process allow groat freedom of 

 protraction and retraction of the lower jaw. Lateral movement is limited. The 

 posterior ligament is absent. 



Dog. — The articular surfaces allow extremely little lateral or gliding movement. 

 They are cylindrical in curvature, and the interarticular disc is very thin. The 

 posterior ligament is absent. 



The other articulations of the skull are sufficiently described in the Osteology. 



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