S78 STERNA OF THE DIVERS, 



tion of half the lineal dimensions of nature, and shown 

 obliquely, half on the under side, half on the profile^ 

 Mill afford a better idea of these energetic careerers 

 through the water than could be obtained from two 

 separate views. 



•On examining this figure, it will be seen that the 

 keel of the sternum, the clavicle, and the scapular of 

 this apparatus, form nearl}^ one continued curve, 

 which does not bear so much on the angle of the 

 keel, and therefore does not press so much upon the 

 sternum, and the viscera which it supports, as in the 

 grebes ; while the sternum, from its greater length, 

 gives more firmness to the under part of the body. 

 The great strain of the shoulder, as the bird moves 

 through the water, is upon the coracoid, chiefly to 

 turn that bone backwards ; and this is resisted by 

 the great enlargement backward at the base, and the 

 embedment of the process of the coracoid and that of 

 the anterior angle of the sternum among the flesh of 

 the shoulder. So that, while the resistance is very 

 powerful, it is at the same time elastic, and not a 

 direct thrust of bone against bone, w^hich would 

 occasion a direct prolongation of the strain through 

 all the bony connexion, instead of an extinguishment 

 of it among the neighbouring parts, as is the case in 

 the mode of articulation here presented. Those 

 direct or jarring strains, propagated all in one direc- 

 tion, are never found in the mechanical structure of 

 animals ; but, on the contrary, the greater the strain 

 upon any one part, the more speedily and widely is 

 it distributed over a number of other parts. 



The form of the clavicle is also a very beautiful 

 part of this structure: the enlargement at the shoulder- 

 joint, the gradual diminution in width as the bone 

 becomes more curved in approaching the keel, and 



