STRUCTURE OF FOSSIL BONE. 69 



bone. There is nothing particnlar worthy of notice on 

 this occasion as to the other bones. 



The structure of the gannet, so far as I have described it, 

 in the principal bones, admirably exhibits the beautiful 

 adaptation of the microscopic structiu*e of bone to the move- 

 ments, habits, and well-being of the creature, and in no bone 

 is that adaptation more clearly shown than in the coracoid 

 — the circular reticulations of the Haversian canals in 

 which bone are assiu-edly designed to enable it to sustain 

 the shock it must receive when the bird impinges on the 

 water ; the powerful bill first cleaves the waves, the strong 

 bows of the furcula next meet the shock, and the injurious 

 eflects of the concussion, which would perhaps be too much for 

 an ordinary coracoid, are obviated by the circular disposition 

 of its Haversian canals. But this is only a single instance. 

 We find wonders of omniscient providence in every skeleton. 

 HoAv admirable is the design displayed in the keel of the 

 sternum. Take that of the heron, for instance ; ths same 

 tender care is shown for the preservation of the bone when 

 acted upon by the powerfid pectoral muscle. It is composed 

 of two plates, with diploe between ; the Haversian tubes in 

 the plates meet the pressure at all points. Examine the tibia 

 of the same bird, and it will be found that they are longitu- 

 dinal in the reticulations. Or if we turn to another kind of 

 bird, the starling, for instance, we find beautiful reticulations 

 in the ulna, with straight Haversian tubes in the coracoid, 

 the very opposite of the gannet. Or if we examine the wang- 

 bone of the razor-bill or guillemot, which is used by the bird 

 to swim with under water, and seldom for flight, we observe 

 not only an external adaptation of the bones, but the micro- 

 scope shows also that there is an internal one as well. And 

 from the numerous observations which I have made, no 

 doubt whatever remains in my mind as to the important ends 

 and services of the Haversian tubes, lacunae, and canaliculi. 



There are not two bones in animals, unless they are of the 

 same kind, that agree perfectly in the arrangement of the 

 Haversian tubes, or even of the lacunae ; hence the certainty, 

 as our knoAvledge increases by careful observations, of ascer- 

 taining the habits of any animal from the microscopic cha=. 

 racters of its bones, a truth which I suraaised and hinted at 

 in a pie^ious paper. 



That the size of the canaliculi is dependent^ as has been 

 supposed, on the size of the blood discs does not appear to 

 be supported by observation ; biit that it is dependent upon 

 the habits and requirements of the animal observation tends 

 to show. The lacunae and canaliculi not being; of universal 



