10 TirE FEATHERED THIBES. 



contiguous tlircads is broken ; wliile if the finger be clrawn up the featlier, tlie threads 

 are restored to their former state. 



Now these effects may be traced to a very beautiful contrivance. The himinoD arc 

 interlaced -n-ith one another, and the interlacing is effected by means of a vast number of 

 fibres or teeth, -which shoot forth from each side of the lamince, and which hook or grapple 

 too-etlicr. These fibres are crooked, but curved after a different mamier. Those whicli 

 proceed from the thread on the side towards the extremity of the feather are longer and 

 more flexible, and bent downwards there, as those which proceed from the side towards 

 the beginning, or quill-end, of the feather are shorter, firmer, and turned upwards. '^Ylien 

 two lamintc are pressed together, so that these long fibres are forced far enough over the 

 short ones, their crooked parts fall into the cavity made b_v the crooked parts of the 

 others — as a latch fastened to a door enters into the cavity of the catch fixed to the door- 

 post, and there hooking itself, fastens the door ; for it is in this manner that one thread 

 of a feather is fastened to another. 



All this the accompanying illustrations will render, wc trust, perfectly clear. The 

 fibrils of a feather from the y,-vag of a goose (fig. 6) are represented magnified at a a, b h, as 

 they arise from the two sides of the edges of each lamina. They arc exceedingly nume- 

 rous, above a thousand being contained in the space of an inch. They are, as is manifest 

 from the engraving, of two kinds, each one having a diSerent form and curvatm-c. 

 Those marked a a, which arise from the side next to the extremity of the feather, are 

 branched or tufted, and bend downwards. Those marked h h, proceeding from the 

 other side of the lamina, or that nearest the root of the feather, are shorter and firmer, 

 and do not divide into branches, but are hooked at the extremities, and are directed 

 upwards. 



The appearance they present will bo seen in fig. 7. It shows distinctly the form, 

 direction, and relative position of each set of fibrils, and the manner in which thej' 

 lay hold of one another. This mechanism is repeated over eveiy part of the feather, 

 and constitutes a closely reticidated sm-face of great extent, admirably adapted to prevent 

 the passage of the air through it, and to create by its motion that degree of resistance 

 which it is intended the -u-iug shoiJd encounter. In feathers not intended for 

 flight, as in those of the ostrich, the fibrils are altogether wanting : in t]u)se of the 

 peacock's tail, the fibrils, though large, have not the construction that fits them for 

 clasping those of the contiguous lamiui-c ; and in other instances they do so very 

 imperfectly. 



Li addition to these parts of a feather, there is what is called the accessory pliuue. It 

 is a small down)' tuft, which not only assmnes a very different cliaracter in tlie feathers 

 of different species, but is even very dissimilar in the feathers of difl;crent parts of the 

 body of the same bird. The accessory plume is situated at the end of the quill fiirthest 

 from the body. In the strong feathers peculiar to the wings and fail it remains a small 

 tuft of down ; but in the feathers of the body, as the hawks, grouse, ducks, gulls, and 

 some others, it is found to be of all sizes. In the ostrich, the feathers have no accessory 

 plume ; hi the rhea there is a tuft of down; in tlie emu the accessory plume is angiuenfed 

 to the full size of the priiieii)al shaft, and the web and the feather of this bird is 

 constantly and correctly represented as haAing two plumes on one quill. In Iho 

 cassowary, besides the double shafts and webs from a single quill, as in the emu, there is 

 still an accessoiy plume, thus fonning throe distinct parts. 



Tlic orn-ans by which the bird rises from the groiuid, and maintains and dii'ccts its 

 aerial pnigression, are, however, the wings and llie tail, and Ihey re(piire of us, tlicreforc, 

 a particidar examination. 



In the wings there is an osseous franu-work, acted upon by nniseles, the tendons of 

 which ure respectively inserted into the several bones composing it, the whole being 



