THE FLEXIONS 



A brief consideration of the bones, joints, and 

 muscles involved in the flexions will help in avoid- 

 ing certain mistakes. 



The bars, on which rest the bits, are the distal 

 part of the lower jaw, between the molar teeth and 

 the incisors. In conformation they are of three 

 types. In one sort the bone is small, and covered 

 by a thin mucous membrane. Such bars are said 

 to be "sharp," and are especially sensitive to the 

 pressure of the bits. Another sort has a large bone, 

 somewhat flattened where it meets the bits, and 

 covered with thick mucous membrane. This sort 

 is commonly little sensitive, and is described as 

 "fleshy." The best type of bar is intermediate be- 

 tween the two. 



The temporo-maxillary articulation which con- 

 nects the lower jaw with the skull lies between the 

 ears and the eyes, just behind the frontal bone. 

 It allows the jaw, moved by the digastricus , mas- 

 seter, and temporalis muscles, to open and shut, to 

 move laterally for mastication, and to glide back 

 and forth. This joint plays an important part in 

 equitation. 



Another important set of bones are the verte- 

 brae of the neck. The first cervical vertebra, the 

 atlas, articulates with the occipital bone of the 

 skull. Next to it comes the axis. These two verte- 

 brae form the atlo-axoid articulation which permits 

 the head to rotate upon the axis, this remaining 

 fixed. The occipito-atloid articulation, on the other 



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