346 



THE MECHANICAL FUNCTIONS. 



one another at angles more acute in these animals than in 

 other tribes of mammalia, so that they are always ready for 

 instantly commencing their flight, and springing forwards 

 on the slightest notice of danger. (See Fig. 218, page 350.) 

 As it was necessary, from the situation of their food, that 

 their heads should reach the ground in grazing, w^e find that 

 the neck has been much elongated, that the muscles which 

 raise the head have been enlarged and strengthened, and that 

 the spinous processes of the back and neck have been much 

 expanded, in order to allow of suiFicient surface for the at- 

 tachments of these muscles. The effort requisite to raise, 

 and even support the head, is very considerable; as will ap- 

 pear when we reflect that its weight acts by means of an ex- 

 tremely long lever; for such is the mechanical office of the 

 elongated neck. But, in order to economize the muscular 

 power, an elastic ligament is employed to sustain the weight 

 of the head. This, which is termed the Ugamentum niichse, 

 and is represented at n, in Fig. 217, is formed of a great 

 number of bands wiiich connect the hinder part of the cra- 

 nium, at the ridge of the occipital bone, and all the spinous 

 processes of the neck, with those of the back, the separate 

 slips from each being successively joined together, and com- 

 posing a ligament of great length and power. It differs, in 



its structure, from ordinary ligaments, being highly elastic, 

 so that it yields to the extension of the neck when the animal 



