i6 A HISTORY OF BIRDS 



has a long unwieldy beak : how could this seize upon and 

 distribute oil over individual feathers drop by drop ? Simil- 

 arly, the Shoveller Duck and the Petrels of the Genus Prion 

 have the edges of the jaws fringed by very long, delicate 

 lamellae : how, with such an armature, could drops of oil be 

 expressed from the gland and spread over the feathers : or 

 how could this be done by the serrated beaks of such birds as 

 the " Saw-billed Ducks '' and the Darters ? The Anastomus, 

 or Open-bill Stork, and the Whale-headed Stork again, would 

 surely find such a feat impossible. And these, be it noted, 

 are all aquatic birds. 



On the other hand, the Bustards, many Pigeons and Parrots, 

 and the Ostriches have no gland : yet they keep their feathers 

 in as good condition as those birds which possess this organ. 

 So copiously is this secretion said to be formed in the gland 

 of the Concave-casqued Hornbill {Dichoceros bicornis) that the 

 feathers of the neck I are said to be stained yellow thereby ! 



Nevertheless, ninety-nine out of every hundred Ornitholo- 

 gists are firmly convinced that they have seen the oil squeezed 

 from the gland, and witnessed its application. 



If, after all, it should be proved that this gland is not used 

 as tradition assures us, what then is its purpose ? So far no 

 really satisfactory hypothesis presents itself. But the same is 

 true of many other glands in other animals. It is possible, 

 however, that it may have served, and may still serve, as a 

 scent gland : though the odour may not be traceable by the 

 olfactory nerves of the human subject, save in one or two cases. 

 In the Hoopoes, for example, it gives forth a most offensive 

 odour, while in the Musk Duck {Bizittra lobatd) it sends forth 

 a musky smell. The peculiar smell of Petrels is also appar- 

 ently due to the secretions of the oil-gland. 



The Skeleton 



Birds show their reptilian ancestry in the skeleton more 

 clearly than in any other part of the body, though even here 

 the evidence has been largely masked by the modifications due 

 to flight. 



The reptilian characters are more conspicuous in the 

 pneumaticity of the bones, the structure of the skull, and the 

 great number of the neck vertebrae, and the structure of the hip- 



