146 THE STRUCTURE OF THE HORSE. 



pouches may become sources of trouble and even 

 danger. As they communicate with the nasal cham- 

 bers by slit-like orifices, when the horse sniffs air is 

 drawn into them. Should this occur when the ani- 

 mal is feeding in a manger or nose-bag, or the food 

 is dusty, minute particles may enter the pouches and 

 set up inflammation, or give rise to the formation of 

 solid concretions. There is reason to believe that 

 millers' horses are more liable to these affections than 



others.* 



The Neck. 



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

 vertebra?, 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 "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 

 of 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 combined action of these numerous 

 joints permits of very free play to the head in all re- 

 quired directions. 



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



