STERNA OF THE PLUNGING BIRDS. 395 



the head of the coracoid, without an object and use 

 in the economy of the bird. 



These birds do not make way with their whole 

 body in the water, as is the habit of the divers ; but 

 they take the water with much more force, and there- 

 fore with a greater shock upon their bodies. Almost 

 all of them plunge headlong on their prey in the 

 water, and some of them do so from a great height — 

 a height from which if even the strongest of the 

 mammalia were to fall on their feet upon the water, 

 they would be in danger of dislocating their joints, or 

 even breaking their bones. All who are in any way 

 familiar with the v/ater must be aware how dangerous 

 it is to descend into that liquid, even from an incon- 

 siderable height, in any other way than head foremost, 

 and especially how very hazardous it is to jump into 

 it from a greater height with the legs apart from 

 each other. Many of the birds of this tribe descend 

 from heights and with velocities which, notwithstand- 

 ing their feathery covering and the yielding nature of 

 the fluid on which they descend, would, if its effect 

 came as a cross strain, break the stoutest bone in 

 their bodies. The bird from its form penetrates the 

 water easily, and the articulations of the neck are so 

 many, and so free in their motions, that any shock 

 which the head may receive by the plunge is so 

 divided among them as not to occasion the least con- 

 cussion of the contents of the skull. Thus the parts 

 v/hich come into the severest contact with the water 

 are the shoulders : and this is met by the strong and 

 comparatively narrow parts of the arches in the direc- 

 tion of the vertical plane. And, upon examining the 

 front view of the sternum, it will be found that, besides 

 the hold which the scapulars have on the back and 

 the stiffness given by the clavicle, the great breadth 



