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 vertebrse, 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- 
* Lufsclika, Dio Halbgclenke des Menschliclien Korpers, 1858, p. 71, and 
Tab. I., fig. 2. 
