212 DETAILED SYNTHESIS. 



303. THE CRANIUM is FORMED by the deposit of 

 earthy matter in a thick membrane, that at the same 

 time loses its fibrous character. 



304. THE PROCESS OF CHANGING THE MEMBRANE into 

 bone is not completed at birth ; hence the soft spot, fon- 

 tanelle, on the top of the head, that gradually closes by 

 the continued process. 



305. THE PROCESS OF DEPOSITING THE EARTHY MAT- 

 TER commences at several points, called points of ossifi- 

 ca^ion, in each (the right and left) bone, and proceeds 

 till the edges of the bone are reached ; and in the outer 

 table, points of an irregular shape mutually extend across 

 the line and interlock, as represented by the sutures. 



Vertebral Column. 



306. THE VERTEBRAL COLUMN is a strong, elastic 

 column of bones called vertebra, and cartilages, from 

 their position between the vertebras called the interver- 

 tebral substances, the whole bound together in addition 

 by numerous ligaments (see Fig. 6, PI. 16). 



307. THE TWO UPPER VERTEBRAE (indeed, they can 

 hardly be called vertebrae) are worthy of a distinct de- 

 scription. 



308. THE UPPER VERTEBRA is CALLED Atlas because, 

 as the god sustained the world, so does this bone sustain 

 the head upon its two shoulders, to which it is so jointed 

 as to allow the nodding motion of the head. 



309. THE SECOND VERTEBRA is NAMED dentatus, 

 from the tooth-like process or pivot that extends up 

 from it through the central hole in the atlas above, a 

 ligament passing across from side to side of the atlas 

 behind the pivot, and thus separating it from the canal 

 proper in which the spinal cord is located. A ligament 

 also extends from the upper point of the pivot to the 



80S. How T 304, What said of ? 805. What is ? 806. What is ? 

 807. What said of-? 808. What ? 809. What-? 



