ANATOMICAL STEUCTUEE OF THE SHEEP. 99 



yellow fat, deposited in fibres of connective tissue. It nourishes 

 the bone, preventing brittleness and dryness. Bones are classed 

 as long, flat or irregular. Under the head of long bones are 

 classed the bones of the limbs, which support and act as levers 

 for the bony framework. Flat bones are found where the 

 least possible motion is desired. They help to enclose cavities 

 containing important organs, such as the brain; or the bones en- 

 closing the cavity of the chest, where the heart and lungs are 

 situated. Irregular bones include all not classed with the long 

 and flat varieties. They are found in the spinal column, skull,. 

 and also in the limbs. They possess as a rule many angles, with 

 surfaces for attachment of tendons and articulating surface. In 

 proportion to their size they present a much greater mechanical 

 strength than those of the other classes. 



Cbc Boms of the r)ead. 



The skull of the sheep articulates with the first cervical verte- 

 brae from which it is suspended by its base. It is composed of 

 a number of distinct and separate bones, which, as the animal be- 

 comes advanced in age, ossify into one solid mass. The first ob- 

 ject of the bones of the skull is to protect the brain from injury. 

 For this purpose the skull surrounding the brain consists of two 

 plates or tables, the outer tough and thick, the inner hard and 

 brittle. The outer, being tough, yields slightly to resistance, 

 diminishing concussion, while the latter, by its hardness, prevents 

 the entrance of sharp bodies into the brain. The cranial cavity 

 containing the brain is about one-third the size of the other parts 

 of the skull, the other cavities being the mouth, for the entrance 

 and mastication of food, and the nasal, for breathing and smell- 

 ing purposes. 



The cranial cavity is formed by the union of nine distinct 

 'bones, cabled respectively 2 frontal, 2 parietal, 2 temporal^ 



