TOUCANS. 



415 



especially in the upper beak ; they are elastic, and yield in a slight degree to mode- 

 rate pressure, but present considerable resistance if a force is applied for the purpose 

 of crushing the beak. At the points of the mandibles the outer walls are nearly a 

 line in thickness ; at other parts, in the upper beak, they are much thinner, varying 

 from one-thirtieth to one-fiftieth part of an inch, and in the lower beak are from 

 one-twentieth to one-thirtieth of an inch in thickness. On making a longitudinal 



O O 



section of the upper mandible, its base is seen to be a conical cavity. The walls of 

 this cone consist of a most beautiful osseous network, intercepting irregular angular 

 spaces varying in diameter from half a line to two lines. From the parietes of this 

 cone, a network of bony fibres is continued to the outer parietes of the mandible, the 

 fibres which immediately support the latter being almost invariably implanted at 

 right angles to the part in which they are inserted. The whole of the mandible 

 anterior to the cone is occupied with a similar network. The air is admitted to the 

 interior of the upper mandible from a cavity situated anterior to the orbit. The 

 nasal cavity has no communication with the interior of the mandible." 



t,- 



FIG. 206. Vertical longitudinal section of the bill of Ramphastos toco, to show the cellular structure of the bill. 

 b. cavity at the base ; d, external nares ; i, cerebrum ; k, cerebellum ; I, tongue ; m, orifice of larynx, n of 

 pharynx ; r, beginning of spinal cord ; s, nasal septum ; tr, trachea ; u, air cell, anterior to orbit from which 

 the air enters the maxilla. 



To facilitate the understanding of the above, we have introduced Fig. 206, in 

 which is also shown the long and peculiar tongue of these birds, which, looked at 

 from above, presents the appearance of a feather, the margin on both sides being 

 obliquely notched, and the notches toward the extremity becoming deeper and closer 

 together, so as to occasion a bristled appearance of the edges. There are many other 

 peculiarities ; but we only mention the fact that the clavicles do not unite at the lower 

 end into a furculum, each one being separately connected with the sternum. 



The toucans have a remarkable habit of turning their tails upon their backs. This 

 is performed with a jerk, " as if on a hinge that was operated on by a spring." In 

 examining the caudal vertebrae, it will be found that the six basal ones are articulated 

 by ball-and-socket joints and connected with the last ones, which are anchylosed, by a 

 synovial joint, and can be bent dorsad till their superior spines touch the sacrum, 

 while the broad and large transverse processes almost wholly prevent lateral motion. 

 The muscles, therefore, which in other birds turn the tail sideways, in the toucans 

 become assistants to the true elevators of the tail ; for when the latter have bent it 

 upwards sufficiently, the former become dorsad of the centre of motion, causing the 



