206 



DETAILED SYNTHESIS. 



279. THE CRANIUM, or brain-case, is arched in all 

 directions in which it is exposed to danger, as that form 

 is the best for resisting the effects of blows. Where it 

 is covered by the facium it is flat and very irregular. 



280. THE THICKNESS OF THE WALLS OF THE CRANIUM 

 varies in different cases and in different parts of the 

 same cranium, from the sixteenth of an inch up to an 

 inch, averaging from an eighth to a half. Those parts 

 are the thickest that are most likely to receive blows, 

 being the back and lower parts. 



FIG. 158. 



Fig. 158 represents a cross section of 

 the Cranium, just in front of its middle, 

 1, the PARIETAL or side bone, jointed with 

 its opposite, above, and below bevelled 

 within the rising wing, 2, of the SPHE- 

 NOID; 3, its level portion; 4, its cells. 

 The proportionate thickness of the Crani- 

 um to its cavity is truthful ; the setting 

 of the arch above within the buttresses, 2, 

 is also excellent. The central dark line 

 in the walls above and below is the diploe. 



281. THE CRANIUM is COMPOSED of three TABLES or 

 plates, an outer or fibrous, an inner or vitreous, and a 

 middle, the diploe. 



FIG. 159. 



Fig. 159 represents the 

 external table removed 

 and the diploe brought 

 into view. It has the 

 same spongiform struc- 

 ture as is found in most 

 bones, with large canals 

 for the location of tubes, 

 as illustrated by the figure. 



279. What form has -? 280. What said of -? Describe Fig. 158. 281. Ilow 

 ? Describe Fig. 159. 



