FREHEXSION OF FOOD. 229 



delicate and complex in the insectivorous species. Serpents crush their 

 prey in their coils before swallowing it. 



All birds use their toothless beaks in procuring food. Birds of prey 

 also seize with their claws, while certain birds, such as parrots and wood- 

 peckers, also employ their beaks as prehensile organs. The beak in birds 

 varies in shape according to their food. Thus, it is short and strong in 

 graniverous birds ; long and slender in insectivorous birds. In birds 

 which catch their prey on the wing, as the swallows, it is short and 

 gaping ; strong and curved in birds of prey which tear their food ; long, 

 conical, and of great strength in borers, as in the woodpecker ; short and 

 curved in the parrot tribe to enable them to crush nuts ; delicate and 

 tapering in humming-birds to allow them to penetrate the corollas of 

 flowers ; long, strong, and pointed in most fish-eaters, as the heron, stork, 

 and king-fisher ; shovel-shaped in many aquatic birds, such as the duck 

 and goose ; or it may be fashioned to hold fish, as in the pelican, albatross, 

 penguins, etc. In the cross-bills the mandibles when closed overlap, 

 a conformation which enables them to extract the seeds from fir-cones. 

 Finally, in the young pigeon, which feeds by placing its bill in the mouth 

 of the mother-bird, the lower mandible is elongated and boat-shaped, and 

 of greater size than the upper. Hence, it acts as a spoon, and becomes 

 relatively smaller as the pigeon grows. In parrots and woodpeckers the 

 tongue is also prehensile. 



The tongue in birds and reptiles, besides being the seat of the sense 

 of taste and an organ of deglutition, is often the sole organ for the pre- 

 hension of food, the mechanisms concerned in this operation, that is, the 

 extension and retraction of the tongue, differing in birds, reptiles, and 

 mammals. In birds the forward and backward movements of the tongue 

 depend upon the muscles which move the hyoid bone. The horns of this 

 bone in birds are arched and extend up behind the occiput, and give 

 attachment to a muscle which is wrapped around them, and is then in- 

 serted in the inferior and posterior surfaces of the rami of the lower jaw. 

 This muscle, which is termed the conic muscle of the hyoid bone (Vicq 

 d'Azyr), by its contraction advances the tongue by bending the arches 

 of the hyoid bone, at the same time drawing them forward. Retraction 

 of the tongue is accomplished by the recoil of the elasticity of the 

 hyoid arches, when these muscles relax, aided by the serpo-hyoid muscles 

 (Duvernoy). These arches are much larger in the woodpeckers than in 

 other birds. 



The mechanism of movement of the tongue in reptiles is much more 

 complicated, and differs somewhat in the four orders of this class. In 

 general it may be said the movements of the tongue in reptiles depend 

 on the two principal means employed separately in birds and mammals ; 

 that is, the intrinsic muscles of the tongue and the hyoid muscles. 



