388 STERNUM OF THE STORK. 



are also necessarily migrant in those parts of the 

 world which are alternately flooded by water and 

 parched by drought. 



The sternum of the cranes is of moderate length, 

 rather narrow, very little hollowed on the upper sur- 

 face, and of nearly equal breadth throughout its whole 

 extent. The sternal crest is large in proportion to 

 the whole extent of the bone ; arched on the under 

 side for the greater part of its length, but slightly 

 concave toward the posterior extremity; and in some 

 of the species it contains a large cavity in which a 

 flexure of the windpipe is lodged, as is also the case 

 in some of those long-necked swimming birds which 

 seek their food with the head immersed in water. 



White stork. 



The angle of the crest advances considerably in front, 

 is rounded, and, in the true cranes, and some other 

 species, united to the central part of the clavicle. 

 Seen in profile, the sides of the sternum appear con- 

 cave ; and in the rear it is divided by two triangular 

 notches, which form the posterior angles into two 

 processes which extend a little, but not much, beyond 



