lO EQUINE ANATOMY. 



detached from bones ; protuberances or tuberosities are large and 

 round ; lines, crests and ridges are narrow and long. 



Cavities of Bones. 



Cotyloid are deeply excavated ; channels or furrows when wide 

 and deep ; fissures when narrow and rough ; digital when of the 

 size of finger-ends ; fossa, sinuses, cells and notches are also cavi- 

 ties. An opening in a bone is 2. foi-amen, if long, a capiat. 



Composition of Bone. 



Bone is composed of one third part animal matter, giving 

 elasticity, and two-thirds ?nineral matter, principally salts of lime, 

 giving strength. 



Structure of Bone. 



Bones are covered externally by a fibrous, nourishing mem- 

 brane, the pei'iosteum. Microscopically bone is seen to consist of 

 the following parts : the medullary canal, see cavity of long bones ; 

 the Haversian canals for the passage of vessels ; lacunce, small 

 black spaces containing bone cells with little canals, the canaliculi, 

 branching from them ; these three structures form the Havei'sian 

 systems. Lamellce are layers of bone under the periosteum or 

 around the Haversian canals. 



The marrow or medulla of bones consist, of red or fatal mar- 

 row, and yellow marrow. The former is rich in round cells, the 

 latter in fat. 



Development of Bone. 



It may be developed from cartilage or membrane. The former 

 method is shown in the long, the latter in the flat bones. 

 Number of Bones. 



Vertebral column 52 



Head 8 



Face < 16 



Hyoid, sternum and ribs 38 



Anterior extremities 40 



Posterior extremities 40 



419 



The ossicles of the middle ear are not included ; the sacrum is 

 considered as five separate bones, the superior turbinated as part 

 of the ethmoid, the pterygoid as a process of the sphenoid, the 

 parietal as a double bone, and the sesamoids are included. 



