268 



THE ARTICULATIONS, OR JOINTS 



ment, the muscles adapting themselves tonically to the length required." 1 Dr. W. VV. Keen 

 points out how important it is "that the surgeon should remember this ligamentous action of 

 muscles in making passive motion for instance, at the wrist after Colics' fracture. If the 

 fingers be extended, the wrist can be flexed to a right angle. If, however, they be first flexed, 

 as in 'making a fist.' flexion at the wrist is strictly limited to from 40 to 50 degrees in different per- 

 sons, and is very painful beyond that point. Hence, passive motion here should be made with 

 the fingers extended. In the leg, when flexing the hip, the knee should be flexed." Dr. Keen 

 further points out that "a beautiful illustration of this is seen in the perching of birds, whose 

 toes are forced to clasp the perch by just such a passive ligamentous action so soon as thev 

 stoop. Hence, they can go to sleep and not fall off the perch." 



The articulations may be arranged into those of the trunk, those of the upper 

 extremity, and those of the lower extremity. 



ARTICULATIONS OF THE TRUNK. 



These may be divided into the following groups, viz. : 



I. Of the Vertebral Column. 



II. Of the Atlas with the Axis. 



III. Of the Atlas with the Occipital 



Bone. 



IV. Of the Axis with the Occipital Bone. 

 V. Of the Mandible. 



VI. Of the Ribs with the Vertebra?. 



VII. Of the Cartilages of the Ribs with 

 the Sternum and with Each 

 Other. 



VIII. Of the Sternum. 

 IX. Of the Vertebral Column with the 



Pelvis. 

 X. Of the Pelvis. 



I. Articulations of the Vertebral Column. 



The different segments of the vertebral column are connected by spinal ligaments 

 (ligamenta columnae vertebralis), which may be divided into five sets: (1) Those 

 connecting the bodies of the vertebra? (inter central). (2) Those connecting the 

 laminae. (3) Those connecting the articular processes. (4) Those connecting the 

 spinous processes. $>) Those of the transverse processes (the last four kinds being 

 known as interneuraT). 



The articulations of the bodies of the vertebrae with each other form a series 

 of amphiarthrodial joints; those between the articular processes form a series of 

 arthrodial joints. 



1. LIGAMENTS OF THE VERTEBRAL BODIES OR CENTRA (!NTERCENTRAL 



LIGAMENTS). 



Anterior Common Ligament. 

 Posterior Common Ligament. 

 Intervertebral Substance. 



The anterior common ligament (ligamentum longitudinale anlerius) (Figs. 

 222, 224, and 228) is a broad and strong band of longitudinal fibres which extends 

 along the anterior (ventral} surface of the bodies of the vertebra? from the axis 

 to the sacrum. It is broader below than above, thicker in the thoracic than in 

 the cervical or lumbar regions, and somewhat thicker opposite the front of the 

 body of each vertebra than opposite the intervertebral substance. It is attached, 



1 Dr. Cleland, in Journal of Anatomy and Physiology, 1866, No. 1, p. 85. 



