THE HEAD AND NECK 



137 



concretions. There is reason to believe that millers 9 

 horses are more liable to these affections than others. 1 



The Neck 



The skeleton of the horse's neck is formed of seven 

 vertebrae, the same number as in man, and, with very 

 few exceptions, indeed, in all other mammals, whether 

 the neck itself be short or long. 



The skull is attached to the first vertebra of the neck, 

 called the atlas, by a deep 6 ball-and-socket ' joint, 

 which allows of motion in various directions, The two 

 projecting condyles of the skull together form the ball, 

 which fits into the hollow front surface ot the atlas. 

 This vertebra also turns freely on the second, or the 

 axis, and there is a certain but more limited amount of 

 motion at each of the succeeding five joints. The com- 

 bined action of these numerous joints permits of very 

 free play to the head in all required directions. 



The neck joins the front end of the thorax or 

 chest, the skeleton of which is formed by the dorsal 

 or thoracic vertebrae above, the sternum or breast- 

 bone below, connected together by the hoop-like 

 ribs. As seen in the figure (Frontispiece), the cer- 

 vical or neck vertebrae are flat above, but those of the 

 thoracic region have long processes projecting up- 



1 See J. Bland Sutton, Evolution and Disease (1890), p. 94. 



