454 Dr. Davy on the Temperature, $c., of Birds. [1865. 



in accordance with a statement that has been made, that the former have 

 a larger proportion of earthy constituents *. 



It may generally be stated, I believe, that the composition and structure 

 of each particular bone has relation to its function, that where unyielding 

 resistance is required, there, cceteris paribus, the proportion of phosphate 

 of lime is largest, as witnessed in the majority of the long bones of the ex- 

 tremities ; that where yielding and elasticity are needed, the proportion of 

 animal matter is somewhat more considerable, as seen in the sternum, cra- 

 nium, ribs, and maxillae. 



Also it may be generally stated, I believe, that in different species of the 

 same family or genus of birds, the composition of corresponding bones 

 varies comparatively little ; and that where there is a variation, it too is 

 connected with use, irrespective of size. And the same remark, I am dis- 

 posed to infer, would be near the truth relative to the proportional weight 

 of the bones in different species. The following results are offered in 

 illustration. 



First, of the cranium. The portion subjected to calcination was that 

 covering the cerebrum. 



grs. grs. 



Buzzard 69 '7 phosphate of lime, 39 '3 animal matter. 



Carrion crow. . . . . 59'5 40'5 



Rook 60-1 39-9 



Jackdaw 59'5 40'5 



Magpie 60'0 40'0 



Owl 57-4 42-6 



Common fowl .... 60'0 40'0 



Common duck 60'0 40'0 



Woodcock 58-2 41-8 



Skylark 63'0 47'0 



Blue tit 58-0 42-0 



Water-ouzel 57'5 42*5 



Godwit, bar-tailed . 60'0 40'0 



Dunlin 67'0 33'0 



Of the above, some of the crania were cellular, others were compact, 

 sinking in water. The crania of the owl and water-ouzel, as already men- 

 tioned, are extreme examples, and yet their proportion of phosphate 

 of lime and animal matter is much the same, both conditions of bone, the 

 very cellular structure of the one, and the compact structure of the other 

 without cells, being suitable to the habits of the individual, in the owl, 

 great strength with lightness ; in the water-ouzel, strength with a compa- 

 ratively high specific gravity. 



The following is the composition of the sternum of a few of the same 

 birds, illustrative of the quality of lightness coupled with a considerable 

 degree of yieldingness, which in the moist bone is very observable. The 

 * Op. cit. p. 69. 



