20 



VERTEBRAL COLUMN. 



and is separated up to the third year by a narrow cartilaginous interval — the 

 iiriiroccntral Kuturc. It would ajrpear further, that while ossification in the centres 

 of the arches commences first in the upper or cervical vertebra3, the osseous 

 centres of the bodies appear earliest in the lower dorsal vertebra;. 



At the time of birth most of the vertebra; consist of three osseous pieces, cor- 

 responding to the three original ossific centres. In the first year of infancy the 

 osseous laminaj of opposite sides become united in a number of the vertebra;, but 

 not in all. The spinous processes, remaining cartilaginous for a time, are gradually 

 completed by the growth of the cartilage and the extension of the bone into 



Fig. 1 /. Fig. 17. — Ossification of the Ver- 



tebra. (R. QUAIN.) 



A, fffital vertebra, showing the three 

 primary centres of ossification ; 1, 2, 

 for tlie pedicles, lamiute, and processes ; 

 3, for the body. 



B, dorsal vertebra from a child of 

 two years ; 1 & 2 are seen to have en- 

 croached upon the body at * the neuro- 

 central suture and into the articular 

 and transverse processes, and to liave 

 united beliind in the spinous process, 

 leaving tlie ends cartilaginous. 



C, dorsal vertebra at about sixteen or 

 seventeen years, showing epiphyses on 

 the transverse processes, 4 & 5, and 

 S2nnous process, (J, and the upper ei^i- 

 physial plate of the body, 7. 



D & E, pai'ts of a lumbar vertebra of 

 about the same age, showing, in addi- 

 tion to the foregoing, 8, the lower epi- 

 jihysial plate of the body ; 9 & 10, the 

 epiphyses of the mammillary tubercl&s. 



them, and at the same time, by the ossific extension of the transverse processes and 

 other parts, the vertebras gradually attain to nearly their full size and shape about 

 the age of puberty. At different periods subsequent to this, five sets of epiphyses, 

 or supplementary centres of ossification, are added. Three of these are small 

 portions of bone, placed on the tips of the spinous and transverse processes : the 



Fig. IS. — Ossification of the Atlas. 



(R. QUAIN. ) 



A, before birth ; 1 & 2, lateral centres 

 of ossification ; the anterior arch is carti- 

 laginous. 



B, in the first year ; 1 & 2, as before ; 

 3, ossific centre in the anterior arch. 



Fig. 19. — Ossification of t]ie Axis 



AS SEEN IN FRONT. (R. QuAIN. ) 



A, from a fcetus of seven months ; 3, 

 the centre for the body ; 4 & 5, two 

 centres for the base of the odontoid pi'ocess. 



B, shortly after birth ; 1 & 2 the lateral 

 centres ; 3, centre for the body ; 6, tlie 

 two centres for the odontoid process now 

 united. 



other two are thin circular plates, one on the upper, the other on the lower 

 surface of the body, chiefly at its circumference. In the lumbar vertebras two 

 other epiphyses surmount the mammillary processes. The transverse process of the 

 first lumbar vertebra is sometimes observed to be developed altogether from a 

 separate centre. Most of the anterior divisions of the cervical transverse pro- 

 cesses are ossified by the extension into them of osseous substance from the 

 neighbouriag posterior part of the process and from the arch ; but that of the 



Fig. 19. 



