CHAPTER XII. 

 THE SKELETON 



OBSERVE that the skeleton as a whole consists of two 

 portions, the Axial Portion, consisting of a central axis, the 

 spinal column, to which the head belongs ; and the Appen- 

 dicular Portion, the limbs and the bones belonging to them. 



In the skeleton as a whole observe : 



1. The skeleton shows the form of the body. 



2. It supports the softer tissues. 



3. It protects softer parts, as the brain in the skull, the 

 spinal cord in the spinal column, the heart and lungs in the 

 thorax, etc. 



4. The bones serve as levers in producing motion and lo- 

 comotion. 



The central part of the skeleton is the Backbone, or Spi- 

 nal Column. As a whole, it is a column, widening toward the 

 base, composed of a series of separate bones called Vertebrae. 



Take a vertebra from the middle of the spinal column : 



1. Its most solid part is its body, or Centrum. 



2. On the dorsal side of this is the Neural Arch, forming 

 with the body the Neural Ring, through which the spinal cord 

 passed. 



3. From this arch there extend projections, or Processes. 

 Hold the vertebra by the tip of its longest process, and place 

 it beside the corresponding vertebra in the complete skeleton. 

 Note that : 



(a) The body is flattened where it fitted against the verte- 

 brae anterior and posterior to it ; 



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