10(3 



GENEBAL OBNITHOLOGY. 



line ; migulated, when they are straight, or nearly so, but do not lie in the same line, and 

 therefore meet at an angle. (An important distinction. See nndcr fomily FringiUidcB iu the 

 Synopsis.) 



II. THE WINGS. 



Definition. — Pair of anterior or pectoral limbs organized for 

 outgrowths. Used for this purpose by bkds iu general ; but by o; 



C 

 A 



Via. 27. — Bones of riglit wing of a duck, CInngvIa islandica. from above, 

 J nut. size. (Dr. K.W. Slmfeldt, U.S..V.) ./, slinuldei-, oiiios : /;, elbow, nncmi; 

 < \ wrist, carpus : 1), end of princil);il finger ; E, end nf hand proper, wi-tacay-pus. 

 A B, upper arm, hrachium ; B (_', fore-arm, antihrachhtm ; CD. whole hand 

 or pinion, manus : composed of C'E. hand proper or mt'tcwarpns, e.xcepting (/-; 

 h' J), or (/ - d 3, d '', fingers, digits. dUjiti. h. Inimi'vus : rd, radius ; ul. ulna ; ,s'o, 

 outer carpal, scapholunare or radiah ; cii, inner carpal, cuiu-ifonue or ulnare ; 

 these two composing wrist or carpus, mc, the compound hand-bone, or mi^fa- 

 carpu.s. composed of three metacarpal bones, bearing ;ts many digits — the outer 

 digit seated upon a protuberance at the head of the metacarpal, the other two 

 situated at the end of the bone. (/ -, the outer or radial digit, commonly called 

 the thumb or poller, composed of two phaiancjes; d^, the middle digit, of two 

 jihalanges; d*, the inner or ulnar digit, of one phalan.x d - is the seat of the 

 feathers of the bastard wing or alula. D to r'(whole pinion), seat of the flight- 

 feathers called primaries ; C to H (fore-arm), seat of the secondaries ,■ .at li and 

 above it in direction of A, seat of tertiarirs proper ; below A, in direction of Ji, 

 seat of scnpu/aries (upon pteryla humeralis). often called tertiaries The wing 

 shown half-spread: complete extension would bring A H C J) into a right line; 

 in ci>mp]cte folding f goes to ^, and Jf to B: all these motions /icarlii in the 

 plane of the paper. Tlie elbow-joint and wrist are such perfect hinges, that, in 

 opening or closing the wing, (' caimot sink below the paper, nor D tly up .above 

 the paper, as would otherwise be the eftect of the pressure of the air upon the 

 Hight-feathers. Observe also: 7y? and »/ are two rods connecting TJ and ('; the 

 construction of their jointing at JJ and C. and with each other, is such, that they 

 can s/ide lei/gflnrise a little upon each other. Now when the point '', revolving 

 about II, approaches A in the arc of a circle, rd pushes on ,sc, while nl pulls back 

 cu : the motion is transmitted to D, and makes this point approach />'. Con- 

 versely, in opening tlic wing, jv/ pulls back sc. and ul pushes on cu, making I) 

 recede from B. In other words, the angle ABC cainiot be increased or dimin- 

 ished without similarly increasing or diminishing the angle Jl CI); so th.at no 

 part of the wing can he opened or shut without automatically opening or shut- 

 ting the rest, — an interesting mechanism by which muscular power is corre- 

 lated and economized. This latter mechanism is further illustrated in llg. 28, 

 where reandiic show respectively the size, shape and position of the radiixl con- 

 dyle and ulnar condyle of the humerus. It is evident that in the fle.xed state of 

 the elbow, as shown in the middle figure, the radius, rd. is si> ivushed upon that 

 its end projects beyond 'j(7,the ulna; while in the opposite comlilion of extension, 

 shown in the lower figure, rd is pulled back to a corrosiJonditig extent. 



flight by means of dermal 

 istriclies and their allies only 

 as outriggers to aid running; 

 by penguins as tins for swim- 

 ming under water ; used also 

 in the latter capacity by some 

 birds thtit My \i'ell, as divers, 

 cormorants, dippers. Want- 

 ing iu iKJ recent birds, but 

 imperfect in a few, as all 

 BatiUe : greatly reduced iu 

 the Emeu, Cassowary, aud 

 Aptery.x ; also in the jMoas 

 (^Diiioniis) ; in the Creta- 

 ceous Hespcrornis only the 

 rudimentary humerns is 

 kuown. To uuderst:ind 



their structure we uiust 

 notice p;irticularly 



The Bony Framework 



(figs. 27, )iS, '29). —The 

 skeleton of a bird's wing is 

 built upou a plan conimou 

 to the fore or pectoral limb 

 of till the higher vertebrates, 

 so that its bones and joints 

 may readily lie compared 

 and identified with those 

 of any lizard or niammal, 

 including man. But the 

 member is highly special- 

 ized; being fitted for accom- 

 plishing flight, not only by 

 the development of feathers, 

 but also by modifications in 

 the bones themselves. 'I'he 

 axes of the bones have a 

 special direction with refer- 

 ence to each other and to 

 the axes of the body ; the 

 movements of the joints are 

 peculiar in some respects ; 

 and the whole extremity of 

 the wiug, from the wrist 

 outward, is peculiarly con- 



