24 



THE BONES. 



CHAPTER IL 

 THE BONES OP MAMMALIA IN PARTICULAR. 



Akticle I. — Yertebeal Column. 



The vertebral column, or spine, is a solid and flexible stalk situated in the middle 

 and upper part of the trunk, of which it forms the essential portion. It protects 

 the spinal cord and sustains the thorax, as well as the principal organs of circu- 

 lation, respiration, and digestion. Articulated anteriorly with the head, and 

 terminating in a point at its posterior extremity, this stalk is formed by a some- 

 what considerable assemblage of short, single, tuberous bones, to which has been 

 given the name of vertehrce. These bones, though all constructed on a uniform 

 type, yet do not offer the same configuration throughout the whole spine. The 

 differences they present in this respect have permitted their being divided inta 

 five principal groups ; whence the division of the vertebral column in five regions, 

 which are, enumerating them from before to behind : 1. Cervical region. 2. 

 Dorsal region. 3. Lumbar region. 4. Sacral region. 5. Coccygeal regioji. The 

 first comprises seven vertebrae, which serve as a base for the animal's neck ; the 

 second has eighteen, against which the ribs are placed ; the third has only six, 

 which correspond to the loins ; in the fourth there are five, constantly fused into 

 one mass in the adult, to constitute a single bone — the sacrum ; while the fifth 

 possesses a variable number of small degenerate vertebrae, gradually decreasing 

 in size to form the tail. The pieces constituting the first three regions are called 

 true vertebrm ; those of the last two are designated /«7se vertebrce. 



The subjoined table indicates the number of vertebrae in each of the regions 

 of the spine, in the horse and other domestic Mammalia. 



The characters belonging to all these vertebrae will be first studied ; then a 

 particular description of those of each region will be given ; and, finally, an 

 examination will be made of the spine as a whole. 



Characters common to all the Vertebrae. 



Each of these small bones is pierced from before to behind by a wide opening — 

 the spinal foramen, or vertebral canal ; whence results, for the entire spine, a long 

 canal traversing its whole length, and which lodges a very important portion of 

 the nervous centres — the spinal cord. This canal, which traverses the vertebrae 



