THE BONES OF THE TRUNK ii 



with bloodvessels. This is knov^Ti as the endosteum or medullary 

 membrane. 



Osseous tissue is richly suppUed with bloodvessels, which are 

 derived from the periosteum and marrow. 



I. THE BONES OF THE TRUNK. 



A. The Vertebral Column. 



The vertebral column is composed of thirty-three vertebrae in the 

 young subject, and these in the adult are divided into two classes, 

 namely, true or movable, and false, immovable, or fixed. The 

 true vertebrae are those which, though connected by hgaments, 

 are quite distinct from each other, so that a hmited amount of 

 movement is allowed between them. The false vertebrae are those 



Pedicle 



Superior Articular 

 Process 



Fig. 6. — The Sixth Thoracic Vertebra (Superior View). 



which, though distinct up to a certain period of hfe, subsequently 

 become ankylosed. The true vertebrae are subdivided into three 

 groups — cervical, thoracic, and lumbar. The false vertebrae are 

 subdivided into two groups — sacral, and coccygeal. 



Component Parts of a Complete Vertebra, — A complete vertebra 

 is composed of a body or centrum ; a neural arch, consisting of 

 two pedicles and two laminae {neur apophyses) ; a spinous pro- 

 cess, or neural spine ; two transverse processes ; four articular 

 processes {zygapophyses), two superior and two inferior ; and a 

 spinal or neural foramen. The body forms the anterior or ventral 

 part of the bone, and is somewhat disc-shaped. The neural 

 arch consists of two halves, the anterior portion of each being 

 the pedicle^ and the posterior portion the lamina. The pedicles 



