THE HEAD AND NECK. 105 



The Skull. 



The general form of the head of the horse is de- 

 termined by that of the skull, which forms its sup- 

 porting framework, and which is of very peculiar 

 and characteristic shape. As in other animals, it is 

 composed of two main portions : (1) the cranium, or 

 skull proper, consisting of a great number of bones, 

 originally quite distinct, but which are eventually 

 firmly united so as to form a solid mass ;* and (2) 

 the mandible, or lower jaw, fastened to the former 

 by a freely movable hinge-joint. 



The cranium is movably joined to the front end 

 of the vertebral column by means of a pair of oval 

 eminences called " condyles," which fit into corre- 

 sponding cavities in the atlas, or first vertebra of the 

 neck. Between these condyles is a large opening 

 {foramen magnum), through which passes out of the 

 cranium the spinal cord, or backward prolongation 

 of the central nervous system, which is expanded in 

 the head to form the brain. 



The cranium may be roughly divided into two 

 portions — a hinder part, or brain-ease, consisting of 

 a solid bony capsule for inclosing and protecting 



* The outlines of the individual bones are perfectly well 

 marked in young subjects, being indicated by fine dividing- 

 lines, called sutures. In old age these often become more or 

 less obliterated by the union of the contiguous bones. 



