8 THE BONES. 



that naturally join the various pieces together are allowed to remain ; and 

 artificial if, after these ligaments have been destroyed, it i^ necessary to 

 replace them by materials foreign to organisation, such as iron or brass 

 wire. 



The skeleton is divided into trunk and limbs. 



The trunk offers for consideration, in the median line, the spine or 

 vertebral column, a flexible stalk measuring the entire length of the animal, ' 

 and composed of a series of distinct pieces articulated one behind the 

 other, Anteriorly, this stalk supports the head, a pyramidal protuberance 

 which itself results from the assemblage of a large number of bones. 

 On each side of the middle portion of the spine, there are detached bony 



arches which have received the name of ribs, and which rest, directly 

 or indirectly, by their inferior extremities, on a single bone called the 

 sternum. These bony arches in this way circumscribe the thorax a 

 spacious cavity destined for the reception of the principal organs of re- 

 spiration and circulation. ° 



The limbs, four in number, two anterior and two posterior are the 

 appendages which support the trunk. Each represents a column divided 

 into several rays restmg upon one another, and generally forming more 

 or less acute angles. The anterior limbs are each divisible into four 

 principal regions : the shoulder, applied against the front part of the thorax • 

 the arm, which succeeds the shoulder ; and the fore-arm and foot The 

 posterior limbs also comprise four regions : the 'haunch or pelvis ' which 

 articulates with the posterior part of the spine ; and the thigh lea and 

 posterior foot. "' 



