THE SKELETON 55 



Body were joined together like the joists and beams of a house, the 

 whole mass would be rigid ; its parts could not move with relation 

 to one another, and we should be unable to raise a hand to the 

 mouth or put one foot before another. To allow of mobility the 

 bony skeleton is made of many separate pieces which are joined 

 together, the points of union being called articulations, and at 

 many places the bones entering into an articulation are movably 

 hinged together, forming what are known as joints. ' The total 

 number of bones in the Body is more than two hundred in the adult ; 

 and the number in children is still greater, for various bones which 

 are distinct in the child (and remain distinct throughout life in 

 many lower animals) grow together so as to form one bone in the 

 full-grown man. The adult bony skeleton may be described as con- 

 sisting of an axial skeleton, found in the head, neck, and trunk ; and 

 an appendicular skeleton, consisting of the bones in the limbs and 

 in the arches (u and s, Fig. 14) by which these are carried and at- 

 tached to the trunk. 



Axial Skeleton. The axial skeleton is made up of the vertebral 

 column or spine, a side view of which is given in Fig. 15; the skull, 

 Fig. 25; the sternum, Fig. 28; and the ribs, Fig. 29. 



The vertebral column is the great supporting center for the whole 

 skeleton and consists of 33 bones grouped as follows from above 

 downward: 7 cervical, 12 dorsal or thoracic, 5 lumbar, 5 sacral, in 

 the adult united into a single bone, the sacrum, and 4 coccygeal, or 

 rudimentary tail bones. 



The vertebral column occupies the mid-dorsal line of the trunk. 

 On top of it is borne the skull (22 bones) made up of two parts ; a 

 great box above, composed of 8 bones, which incloses the brain 

 and is called the cranium; and a group of 14 bones on the ventral 

 side of this which form the skeleton of the face. Attached by liga- 

 ments to the underside of the cranium is the hyoid bone, to which 

 the root of the tongue is fixed. There are 12 pairs of ribs, at- 

 tached dorsally to the 12 thoracic vertebrae, one pair to each ver- 

 tebra. The sternum, which occupies the mid-ventral line of the 

 thorax and constitutes the anterior attachment for the ribs is made 

 up of two bones, the manubrium and the body, and a cartilage, the 

 ensiform cartilage. 



Details of the Vertebral Column. The vertebral column is in a 

 man of average height about twenty-eight inches long. Viewed 



