FEATHERS AND THEIE ARRANGEMENT. 5 



needed for the purpose of bearing feathers, are also small. One of them is composed. 

 of either two or three joints, but the other is a very little one, being but one single 

 pointed bone. 



The bones of the legs are very similar in their arrangement to those of the mammalian 

 quadrupeds, although they are subject to certain modifications, especially at their 

 extremities. The thigh-bone is tolerably strong and cylindrical, but of no very great 

 length, in proportion to the size of the bird or the length of its limbs. Even in the 

 curious stilt-plover, where the legs are of such extraordinary length, the thigh bone 

 is comparatively short, and not visible outside the feathers. The leg bone, or " tibia," is 

 always the largest bone of the limb, and is accompanied by a very small and undeveloped 

 " fibula," which is only attached to its upper extremity, and tapers gradually to a point. 

 The "instep," as we should term it in a human foot, is merely a single bone, jointed at its 

 upper extremity to the tibia, and its lower to the bones of the toes. In general, birds are 

 furnished with four toes on each foot, but there are several exceptions to this rule, among 

 which the ostrich is the most conspicuous. 



Not only do the bones of a bird differ in external form from those of a mammal, but 

 they are also considerably modified in their structure. In the mammals the bones are 

 heavy, solid, and their centre is filled with marrow ; but in the birds the bones are of a 

 much lighter make, and many, such as the upper wing bone, the breast bone, and part of 

 the skull, are, moreover, hollow throughout their centres, so as to combine great strength 

 with the least possible weight. These hollow bones communicate with the legs through 

 certain curious appendages called air-sacs, which open into the lungs, and apparently serve 

 as reservoirs of respirable atmosphere, so that the bird is able to force the hot and 

 rarefied air from its lungs into its bones. In some very rare instances even the bones of 

 the feet and toes are hollow, and penetrable with air as far as the insertion of the claws. 

 Some birds, however, especially those of small dimensions, do not possess these hollow 

 bones, and in all cases the cavity is not developed until the creature has attained to 

 maturity. In the apteryx, a non-flying bird, the only hollow bone is that of the lower 

 jaw. So complete is the communication with the lungs through the bones of some birds, 

 that if the bone should be broken they are enabled to breathe through the open extremity, 

 even though the throat be compressed, or the head plunged under water. 



This slight sketch of the skeleton is necessary as a prelude to the description of the 

 Feathees, because several of the most important of these appendages derive their names 

 from the portion of the structure on which they are set. 



On a general view of a bird it will be seen that the feathers fall naturally into two 

 orders, namely, those of progression and those of covering. But as in the description of a 

 bird, especially of one that is unknown to science, and of which no figure is extant, it is 

 needful to describe the form and colour of the different portions of the creature with great 

 accuracy, this sweeping division of the feathers into two sets will be quite insufficient for 

 the purpose. On a closer examination, however, it will be seen that the_ feathers possess 

 a kind of natural arrangement, which, with a few unimportant and obvious additions, is 

 amply sufficient for actual scientific purposes. The best mode of learning the name_ of 

 the different parts of the plumage is to procure any bird, say a sparrow or pigeon, which 

 may easily be obtained, and to investigate the formation and arrangement of the feathers 

 from actual inspection. It is an interesting little study, and will save much time, as a 

 lesson once so learned will never again be forgotten. We will suppose a dead sparrow to 

 be laid on the table. 



Let one of its wings be spread upon the table, and its plumage will be seen to consist of 

 a row of long, flat, and stiff quill feathers, whose insertion is covered by a great number 

 of smaller and softer feathers. The quill feathers are technically termed " principals," 

 and the others are called from their office, " coverts." Before examining the principals, it 

 needs that the coverts be first attacked, because they must be removed before the quill 

 feathers can be properly traced to their sources. Along the upper surface of the wing 

 run two or three rows of these short feathers, which are termed the " greater coverts," 

 and below these a single row of " lesser coverts," the latter of which may be distinguished 



