108 THE MECPIANICAL FUNCTIONS. 



back and neck to be fixed to the head, and to 

 support its weight when tlie animal stoops to 

 graze. This, the ligamentum nuclicB, as it is 

 termed, is capable of great extension, and by 

 its elasticity reacts with considerable force in 

 recovering its natural length, after it has been 

 stretched. This ligament is particularly strong 

 in the Camel, whose neck is of great length.* 

 Another example of an elastic ligament occurs 

 in that which connects the two shells of bivalve 

 mollusca (as those of the oyster and muscle), and 

 which keeps them open when the animal exerts 

 no force to close them. The claws of the Lion, 

 and other animals of the cat tribe, are retracted 

 within their sheaths by means of two strong 

 elastic ligaments. Structures of this kind are 

 employed very extensively in the fabric of in- 

 sects-t 



* Many birds are provided with strong elastic ligaments con- 

 necting the vertebrse of" the neck with those of the back ; liga- 

 ments of the same kind are also employed for retaining the wings 

 close to the body, where they are not used in flying: and a 

 similar provision is made in the wings of bats. The weight of 

 the bulky organs of digestion in herbivorous quadrupeds require 

 some permanent support of this kind ; and this is furnished by 

 a broad, elastic, fibrous band extended across the lower part of 

 the abdomen. It is particularly strong in the elephant, which 

 remains more constantly in the horizontal position than most 

 quadrupeds : and it has been remarked that the general cellular 

 texture in this animal has an unusual degree of elasticity. — 

 Hunter on the Blood, &c. p. 112. 



+ Chdbrier, Memoires du Miisee, torn. vi. p. 416. 



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