146 COMPARISONS OF STRUCTUUE IN ANIMALS. 



Of the caudal vertebra of birds little need 

 be said ; they are small with marked spinous 

 processes, but the last is enlarged and com- 

 pressed, and termed the ploughshare. The 

 vertebras of the neck, however, require jnore 

 consideration. If we except the parrot and a 

 few more birds, the only organ of prehension 

 which these animals possess is the bill, and in 

 connexion with this the neck may be regarded 

 as a sort of flexible arm ; wthout it, the use 

 of the bill would be very limited. It is by 

 means of his long slender neck, that the 

 patient heron darts his beak with arrow-Hke 

 rapidity at passing fish. The swan is enabled, 

 by means of hife long neck, to explore the 

 muddy bottom of the lake or river; and, even 

 in birds with far shorter necks, which feed in 

 a similar manner, §till a certain degree of 

 length, and great mobility, are necessary. It 

 is among the waders, and the duck tribe in 

 general, that we find the neck the most elon- 

 gated, and the vertebras composing it the most 

 numerous ; for, be it observed, the vertebra 

 composing the part in birds are very variable. 

 In the swan, there are twenty-four cer^-ical 

 vertebra ; according to Cuvier, the stork and 

 crane have nineteen cervical vertebrfe : in the 



