40 GENERAL ANALYSIS. 



behind to form the spinous processes or spines, thus 

 leaving a hole through each and throughout the spinal 

 column, forming a very important, well-protected canal, 

 called the spinal canal. (See Figs. 60 to 63.) 



60. THE COSTAL PORTION OF THE TRUNK-WALLS 

 MUST HAVE FOB ITS FRAMEWORK a strong yet slightly 

 flexible set of levers; for though the springs or interver- 

 tebral substances of the spinal column will yield, they 

 must be quite firm in order to support their burdens, and 

 therefore not made to yield without considerable force; 

 and the head is so much elevated that it acts with a 

 great purchase or leverage, and long levers are required 

 to stay it. 



Gl. THE RIBS are levers of a peculiar form, attached 

 by movable joints to the spinal column, and curving 

 around and downward : all but the lower ones are very 

 flexibly attached to the breast-bone or sternum in front, 

 thus forming the movable and flexible framework of 

 the sides of a box, the passive elastic character of which 

 will be found of as much use as the activity conferred 

 by its muscles when they are added. 



f Pelvis. 



FRAMEWORK OF TRUNK-WALLS . . J *Pmal Column. 



I KIDS, 



[Sternum, or breast-bone. 



62. THE ABDOMINAL PORTION OF THE TRUNK-WALLS 

 has no framework, except as the ribs above and the pel- 

 vis . below may be considered as such, but is composed 

 of the muscles, nerves, skin, and blood-tubes, that close 

 across from the pelvis up to the ribs. 



63. THREE CAVITIES EXIST WITHIN THE TRUNK- 

 WALLS, corresponding to the Pelvic, Abdominal, and 

 Costal or Chest- Walls, and similarly named. The for- 

 mer two are not divided internally, both being usually 

 called as one, the abdominal ; the two latter are parted 

 by what is called the Diaphragm. 



Describe Figs 58 to 65. 60. What must ? 61. What arc ? Write oat ta- 

 ble of. 62. How is composed ? 63. "What ? 



