THE SUPPORTING TISSUES. 



77 



Bony Tissue. 



Osseous tissue is familiar to every one as the tissue of 

 which bone is composed. The bones of the body in their 

 proper articulations form the skeleton. The skeleton con- 

 sists of a trunk, two pairs of extremities, their supporting 

 girdles, and the skull. 



The trunk is composed of seven cervical vertebrae, twelve 

 dorsal, five lumbar, the sacrum, and the coccyx. 



VERTEBRA. 



The first vertebra called the 

 atlas differs from the rest in that 

 the body of the atlas has grown to 

 the next vertebra, the axis, forming 

 a pivot, the odontoid process on 

 which the head turns. The cervi- 

 cal vertebra has a few characteris- 

 tics by means of which it may be 



Cot) 



4V 



Fig. 19. SPINAL COLUMN. 



(vSide view.) 



(', cervical; D, dorsal; L, 

 lumbar; S, sacrum; Co, 

 coccyx. 



Fig. 20. ATLAS. (Seen from above.) 

 Dotted lines, position of transverse ligament to 

 hold in place the odontoid process ; oblique line, in- 

 sertion of ligament into a bony tubercle; other lines, 

 articulating surfaces. 



Fig. 21. ATLAS AND AXIS, FRONT VIEW. 

 Upper line, odontoid process; remaining lines, 

 articulating processes. 



