﻿EXTERNAL ANATOMY. FEATHERS. 77 



also remarkably conspicuous upon the breast of the herons, 

 where it exists unmixed with any other feathers, and 

 contains, moreover, a white powdery substance, the use 

 of which is unknown. It is curious that the breast of 

 the herons should have a protection of this kind, when the 

 back of their neck, which is equally destitute of true 

 feathers, has none. But it is obvious, from the wading, 

 habits of these birds, that their breasts are much more 

 likely to come into contact with the water than the back 

 of their necks, seeing that the latter part is only thrown 

 out and extended for a moment when the bird suddenly 

 seizes its prey, whereas the breast, if the bird is wading, 

 may be exposed for some time to the action of the water. 

 Birds, whose bodies are supplied with a great quantity 

 of down, instinctively employ it to line their nests, as 

 the eider is well known *to do. 



(71.) The regular external feathers of the body, 

 like those of the wings and tail, are very differently con- 

 structed from such as are called the down ; they are 

 externally composed of three parts or substances : 1. The 

 down ; 2. The laminae, or webs ; and, 3. The shaft, or 

 quill, on the sides of which the two former are arranged. 

 The downy laminae, or webs of these feathers, are very 

 different from the substance we have just described, since 

 they not only have a distinct shaft of their own, but the 

 laminae which spring from both sides of it are percep- 

 tibly and regularly arranged, although, from being devoid 

 of all elasticity, like true down, they do not unite and re- 

 pose parallel to each other. The soft downy laminae are 

 always situated close to the insertion of the quill into the 

 skin ; and although, for obvious reasons, they are more 

 developed on those feathers which cover the body, they 

 likewise exist on such as are employed in flight, as 

 shown in the quill of a goose ; and as they are always 

 concealed from sight when the plumage is uninjured, 

 and are not exposed to the action of the air, so they are 

 always colourless. The third part of a feather consists in 

 the true external laminae, which are arranged in two 

 series, one on each side the shaft; and these sides 



