144 COUES ON THE OSTEOLOGY 



Sacral vertebra:. I have been unable to determine the exact number of vertebras which 

 compose the sacrum. Including the first three costiferous ones, the number is apparently 

 about fifteen. They are throughout completely consolidated with each other, not only by 

 their bodies, but by their processes, especially the dorsal spinous ones. The sacrum thus 

 formed is exceedingly long and remarkably narrow in shape ; having a lateral anchylosis 

 with the iliac bones for nearly its whole extent. It is largest and stoutest opposite the 

 acetabula and just posterior to them ; where not only the bodies of the vertebras are 

 enlarged, but the long bony ridge produced by the perfect union of the dorsal spinous pro- 

 cesses becomes widened and thickened. This long bony spine has but a slight curvature ; so 

 that while just posterior to the acetabula it is scarcely above the level of the iliac bones, 

 yet at both extremities it is elevated some distance above them, by the convexity which 

 their upper border presents. On the ventral surface of the sacrum its first three vertebras 

 have their bodies laterally compressed, so that a median ridge is produced analogous to 

 that of the dorsal vertebras. The transverse processes are also tolerably distinct. Just 

 posterior to the acetabula, however, the transverse processes are hardly traceable, and 

 the body of the sacrum has a median longitudinal furrow, instead of a ridge ; more pos- 

 teriorly again, the median ridge reappears, and the transverse processes become evident, 

 intimately joined with the united ilia and ischia, each one separated from the next by 

 an oval foramen. 



Coccygeal vertebra;. There are seven bones in the coccyx, all freely movable upon each 

 other. The first two are included between the projecting tubera ischii, which their trans- 

 verse processes almost touch. Leaving out of consideration the coccygeal vomer, the 

 bones have all the processes of the vertebras of the other portions of the column. The 

 transverse are largest on the fourth and fifth, becoming smaller both anteriorly and pos- 

 teriorly. The superior spinous processes are well developed, the more anterior ones 

 terminating by tuberculated extremities, which gradually grow smaller, till the last one is 

 a simple thin lamella of bone. The inferior or ventral processes are rather stout thick 

 tubercles than spinous processes ; they are largest posteriorly, and decrease rapidly in size 

 from behind forward. 



The "vomer" is of moderate size. Its proximal extremity is deeply concave, bearing 

 in its centre the round articulating facet. The thickening of the bone which forms this 

 facet is continued along the middle of the bone to the extremity, as a prominent longitu- 

 dinal lateral ridge. The superior border is very thin and sharp, nearly straight in outline; 

 the inferior border curves gently upwards, and is thickened. The distal extremity is 

 simply a small convex nodule, with no projecting process. 



Ribs. The ribs are ten in number. Of these nine articulate with the spine, and 

 eight with the sternum. Seven only are dorsal ribs proper ; the eighth and ninth being 

 articulated with the sacral vertebras posterior to the tip of the crista ilii, and the tenth being 

 connected neither with the spine nor sternum. 



The determination of the first rib is rendered very easy and certain, by reason of the 

 styliform processes or " rudimentary cervical ribs" decreasing rapidly in length from the 

 cranial to the caudal end of the cervical vertebras ; so that on the last two or three they 

 are merely slight pointed tubercles. Then from the first dorsal vertebras the first rib pro- 

 jects as a very slender delicate pointed spicula of bone about two inches long, not reaching 

 much more than two thirds the way to the sternum, terminating by a free unattached ex- 

 tremity. This rib is also remarkable for the shortness of its neck, and the consequent close 



