224 Proceedings of the Royal Physical Society. 



the succeeding vertebrae, except only that the odontoid pro- 

 cess is superadded to the centrum ; and the bulging of the 

 arch on each side behind the transverse process is well 

 marked, and bears the inferior articular surface on its under 

 side. On the. other hand, the superior articular surface is 

 placed partly on the odontoid process, but principally on the 

 most anterior part of the arch, viz., that part which, in all 

 the succeeding vertebrae, forms the posterior angle of the 

 body (fig. 3). So also on the anterior extremity of the arch 

 are placed the articular surfaces (both superior and inferior) 

 of the atlas (fig. 4) ; and also, in the dorsal region, the sur- 

 faces for the heads of the ribs. The occipital condyles are 

 placed upon the most anterior parts of the arch of the occi- 

 pital bone, and to a small extent upon the centrum. 



The foregoing examination of vertebral articulations leads 

 us to observe, that, when surfaces for a synovial joint are 

 present upon the body of a vertebra, however little of the 

 body they may cover, they are never absent from those 

 angles which are formed by the arches. 



The synovial articulations between the bodies of vertebrae 

 in mammals are arranged in the following manner: In the 

 dorsal region are the synovial capsules for the heads of the 

 ribs, which always occupy the angles of the bodies, but are 

 also, in many animals, united across the middle line between 

 the intervertebral disc and the conjugal ligament ; while in 

 some cases, as in the horse and the sheep, a small line of 

 cartilage is stretched along the superior margin of the pos- 

 terior of the two vertebrae concerned in each joint. In the 

 cervical region in the human subject, the minute joints de- 

 scribed by Luschka,* are situated between those parts of the 

 bodies which are formed by the arches. Lastly, in the atlo- 

 axoid and atlo-occipital articulations, the principal parts of 

 the articular surfaces are placed upon those parts of the 

 arches which correspond to the angles of the bodies of 

 succeeding vertebrae, while the intervertebral discs have 

 disappeared. 



I may here remark that, if the odontoid process be re- 



* Lusclika, Die Halbgelenke des Menschlichen Korpers, 1858, p. 71, and 

 Tab. I., fig. 2. 



