24 SKETCH OF THE ANATOMY OF THE HORSE. 



CHAPTER IV. 



SKETCH OF THE ANATOMY OF THE HORSE, 



Definitions— Bones— Joints and Ligaments— Muscles— Heart and Lungs- 

 Nervous System of the Horse. 



Definitions.— When one bone unites with another bone, or with a 

 piece of cartilage, to form a joint, it is said to mticulate with it The 

 ternx arhadafion is used as a synonym ioT Joint, 



A ball and socket joint is formed by the head of one bone resting in 

 a cavity of another bone. The more shallow the cavity, the more ex- 

 tensive will be the power of movement. The horse's shoulder joint and 

 hip joint are good examples of this kind of articulation. A hinge joint is 

 one which works only by extension and flexion, like the horse's knee. 



"A limb," as Professor Huxley states, " is /«f^<?^ when it is bent; 

 extended, when it is stiaightened out." We may adopt this definition, with 

 the exception that the fetlock joint becomes bent when it is extended, and 

 •straightened out when it is partly flexed. 



The word dorsal is used with reference to things of, or belonging to, 

 the back, which, anatomically, is limited to that portion of the spine 

 which is connected with the ribs. 



If a muscle is attached, by one end, to a bone which it can move, and, 

 by the other end, to one which is fixed, the former is called the insertion of 

 the muscle ; the latter, the origin. Thus, the origin of the biceps in man 

 {p. lo) is near the shoulder joint ; and its insertion is on the bone of the 

 fore arm. When a muscle, on contracting, can move the bones at both its 

 ends, the points of connection are called attachments ; an expression which is 

 also apphed collectively to the origin and insertion. I may mention that 

 muscles are not invariably attached to bones, but may, on the contrary, be 

 connected to cartilages, ligaments, to the fibrous covering of muscles, or even 

 to the skin. 



Bones. — ^The skeleton is composed of the hmbs and spinal column, 

 which consists of the head, vertebrae, ribs, and breast-bone (Fig. 12). A 

 vertebra is one of the short bones which, when united, form the column 

 of bones that extends from the head to the end of the tail. There are seven 

 vertebra of the neck, eighteen of the back, six of the loins, five of the croup 



