1865.] Dr. Davy on the Temperature, $c., of Birds. 455 



perpendicularity of the crest or keel of this bone, I may remark, is very 

 characteristic of the equality of action of the great pectoral muscles attached 



to it. 



grs. grs. 



Buzzard .......... 55 phosphate of lime, 45 animal matter. 



Stork ............ 54 46 ;, 



Carrion crow ...... 54 46 ., 



Jackdaw ........ 55 45 



Skylark .......... 58 42 



The composition of the maxillae of a very few birds is given illustrative 

 of the same quality. The lower jaw has been selected, and it has been 

 divided, its anterior portion deprived of its horny integuments ; its posterior, 

 including its head, have been taken for the sake of comparison, the one 

 being more elastic than the other. 



Here I would beg to offer a few remarks more on the subject of the bones 

 of birds. It is stated, and by so high an authority as Professor Wagner, 

 that their hollow bones are whiter than those filled with marrow. Gene- 

 rally this is a fact, and for the reason that, being translucent, the latter owe 

 their colour to the marrow within them. Accordingly their colour varies 

 with the colour of the marrow. Thus in some in which the marrow is of a 

 light hue, almost white, as in the instance of the tawny owl, its ulnse and 

 radii are so white as to suggest their containing air. In another (the yel- 

 low-hammer), in which the marrow is of a bright yellow, as is also the fat, 

 the long bones have the same hue. The same hue is seen in the bones of 

 the cuckoo, and from the same cause, and also, but in a less degree, in 

 those of the greenfinch. Nor are there wanting examples of a dark colour 

 of the bones, from a dark colour of the marrow : those of the little sand- 

 piper may be mentioned as an instance. Generally it may be remarked 

 that the femora are darker than the humeri ; and that the lower portion of 

 the tibiae is very much lighter than their upper, corresponding to the colour 

 of the marrow in each. Another circumstance influencing the colour of 

 the bones of birds is the degree of thickness of their walls. The thicker 



* The bone of the under bill of the godwit, like that of the majority of the long-billed 

 birds, is very slender and remarkably elastic, especially its anterior portion, that which 

 is covered with integuments and a hard horny cuticle ; the same portion is cellular and 

 very vascular, suitable for renewing the growth of the beak as it is wasted in use, a 

 remark more or less applicable to the beak of birds generally. 



