—_- 
Breast-Bone of the Gannet. 43 
they project somewhat from the sides, and during the plunge 
they are forced by the pressure of the water tightly against 
the body, and backwards towards the tail. Nearly the whole 
of the strain which is thus caused, and which must often be 
very considerable, especially when the Gannet is fishing in 
rough weather, is necessarily thrown upon the shoulder joint, 
and but for the arrangement next to be described it would 
probably often be sufficient to disable the bird. From the 
front part of the body of the sternum is developed a very large 
and powerful wedge of bone, and on the sides of this wedge 
the coracoids are articulated, not, as in nearly all other birds, 
at right angles, or nearly at right angles with the axis of the 
sternum, but in a direction nearly parallel with the axis. 
When, therefore, the strain begins to be felt at the shoulder 
joint the coracoids slide slowly backwards down the sides of 
the wedge of bone and ease the strain. This allows the wings 
to perform a similar movement along the sides of the body, 
the front part of which forms a flattened cone, round the sides 
of which the wings are wrapped. By this exceedingly simple 
and yet beautiful mechanical contrivance of a wedge within a 
cone the pressure of the water is gradually eased off and 
reduced to nothing, and this without any undue or dangerous 
strain being placed upon a single muscle or ligament. The 
very strong clavicles and the thick coating of feathers which lies 
between the wing and the body must both play an important 
part in easing off the effect of the blow caused by the bird 
striking the water. The clavicles, being fused to the end of the 
ridge of the sternum, would act as a spring, much in the same 
way as the top joint of a salmon rod, whilst the feathers 
would act as padding and help to prevent any jar. The 
breastbone of the Gannet which I have here is the one which 
I took out of the Gannet which I dissected in December, 1876. 
I gave this to Dr. Rolleston for the University Museum at 
Oxford, and he has very kindly lent it to me for exhibition this 
evening. 
