THE OOLOGIST. 



145 



feather, you will have noticed, bends 

 easily in the direction of the web, but 

 on attempting to bend it backwards or 

 forwards we find it is quite rigid. 

 Upon the examination of a cross section 

 of the shaft, beneath a microscope, the 

 reason is at once apparent. The shaft 

 like the quill is a horny sheath or tube, 

 thick and hard upon its front and back 

 faces, but compartively thin upon the 

 sides, from which springs the web. 

 This sheath is filled with myriads of 

 pithy cells. vei*y much resembling hon- 

 ey comb, but so small as to be invisible 

 to the naked eye. 



The web of the feather is composed 

 of a number of elastic strips, arranged 

 in a single series on each side of the 

 shaft, and inclined toward it. These 

 strips, or barbs as they are commonly 

 called, are mere prolongations of the 

 outer coating of the shaft, and are 

 somewhat wider at the base than at 

 their extremity. 



From the sides of the barbs, and in 

 the same manner as they arise from the 

 shaft, there spring immense numbers 

 of small filaments known as barbules. 

 Again calling our microscope into re- 

 quisition, we find that these barbules 

 consist of a thin, semi-transparent 

 blade, along one edge of which there 

 runs a heavy rib, the whole presenting 

 a striking resemblance to a scythe blade. 

 The main difference being, that in the 

 barbules the rib extends some distance 

 beyond the blade, and is fitted at its 

 free extremity with a number of hooked 

 spines, arranged in a series much like 

 the teeth in a comb. The use of these 

 hooks will appear presently. Place 

 two feathers side by side so that their 

 webs oveidap slightly, and you will 

 notice that their barbs cross at almost a 

 right angle. In the same manner the 

 barbs being side by side upon the shaft, 

 the barbules springing from the right 

 hand side of the first barb overlap, at 

 right angles, the barbules springing 

 from the left hand side of the second 



barb, in the same* manner as those 

 springing from the right hand side of 

 the second barb, overlap those on the 

 left of the third, and so on till the tip of 

 the feather is reached. The before 

 mentioned series of hooks upon the 

 overlapping barbules, interlocking so 

 firmly, that a close and compact surface 

 is formed. 



The wing and tail feathers are of this 

 description, while those covering the 

 body are usually somewhat different. 

 The quill, shaft and barbs, are more 

 soft and elastic, the barbules become 

 round and thread-like, and there is 

 scarcely any appearance of hooks' But 

 feathers may be found upon almost any 

 bird, ranging anywhere between this 

 and the first mentioned. 



Another feature of the body feathers 

 on many birds, is the pleumule or ac- 

 cessory-plume. This is a collection of 

 loose wavy barbs, ranged about the 

 junction of the quill and shaft. It var- 

 ies much in size upon different species, 

 and even upon different parts of the 

 same bird, and is not found upon either 

 wing or tail feathers. Upon this access- 

 sory-pluine, as well as the elasticity and 

 lightness of the shaft and barbs, de- 

 pends very much the value of bed 

 feathers. 



Some birds more especially aquatic 

 species, having no accessory plume, are 

 furnished with a downy covering be- 

 neath their ordinary plumage. This 

 covering is composed of very small 

 tubes lying in the skin, from the interior 

 of which there arises a tuft of filaments, 

 forming a warm coat without appre- 

 ciable weight. 



Feathers possess a few other gradua- 

 tions in structure which are unique and 

 curious. The Cassoway, instead of or- 

 dinary plumage, is furnisned with a 

 number of cylindrical tubes, which are 

 merely quill and shaft, entirely desti- 

 tute of barbs. The Bohemian Waxwing 

 and our common Cedar Bird, bear at 

 the ends of their secondaries, horny 



