PASSEHES. 459 



In the patagium, that is the triangular membrane of the bird's wing expanded 

 between the anterior margins of the humerus and tlie fore-arm, the tendons of two 

 muscles are to be found. One is that of the tensor ^Mtcif/u lon(/us, which forms the 

 su])i)ortiug chord of the free margin itself. The second is that of the tensor patagii 

 brevis, which courses j)arallel willi the humerus from the shoulder to the muscles and 

 fasciaj of the fore-arm. From the comparatively insignificant fleshy belly of this 

 muscle, a single cylindroid tendon runs to the upper margin of the a.xially running 

 tendon of origin of the extensor metacurpi radkdis Ioikjus, at a point not fai- from 

 the tubercle on the humerus, whence this muscle springs. In most of the Passeres the 

 tensor patagii brevis here becomes attached to the latter nniscles without blending 

 with its tendon, and runs from the point of attachment back, indej)endontly )i,\ing 

 itself to the base of the same tubercle as the extensor m. r. longus, as a consequence 

 of which arrangement two distinct tendons run to that same spot, as may be j)lainly 

 seen in the accoiiii>aiiying cut (Fig. 'J"J8 A.) In a few Passeres of the South American 

 families Pteroptochidas and Conopophagida;, the arrangement is a little obscured since 

 the muscular fibres of the extensor m. r. longus almost surround and enclose the ten- 

 dons in question, but upon removing these covering fibres the two tendons are seen 

 arranged exactly as in most other mcTubers of the order. The only real exceptions 

 are tiie lyre-bird {Jlenura}, and the Australian brush-bird Atrichornis ritfescens, in 

 which the tensor brevis inserts itself on the tendon of the extensor metacarpi, in such 

 a way as to blend with it entirely, only one tendon running to the tubercle at the 

 elbow, an arrangement which is exactly like that of the Kamphastida;, Megalaimidie, 

 Indicatoridse and Picidie of the foregoing order, and illustrated in Fig. 228 B. 



A certain structure of the syrinx is also peculiar to the Passeres, although not 

 common to all of them. Having already in the introduction to this volume promised 

 a fuller account of this feature, we shall try to make this point as intelligible as pos- 

 sible, especially since the syringcal arr.angement ; ; 

 has been made the chief character by which some 

 systematists ])rimarily subdivide the Passeres. 



The great German anatomist, Johannes 5Itll- 

 ler, in 184G announced the discovery that the 

 Passerine birds exhibited two — or rather three 

 — radically different types of the lower larynx. 

 He found that in the vast assemblage of birds 

 which has usually been called Oscines, Cantores, 



etc., the intrinsic muscles — numbering from ^^^ „„^ _ j,^._.„,^ ,^, „, Airu-hom,. (acromy- 

 two to six: pairs — are inserted into the extremi- O'l'^'n) ."'"'. i") ».' '/*'"<■''■» ,<"'*'*"™>i'*''""i ■ri 



' extrinsic, i, intrinsic muscles ; s, broncbial 



ties of the bronchial S(ini-rin"S, an arrano-cment «cmi-iiiii;s , 1, trachea ; the muscles are lined 



■" ^ lungitiitlinallv. 



which Garrod has termed acromijodous, while 



the rest have these muscles — usually only one pair — attached to the semi-rings in 

 their middles; these are called Mesomyodi, or Clamatores. But of the latter some 

 South American forms are j)eculiar in having the syrinx chiefly formed by the lower 

 end of the trachea, hence Mullcr made them a separate group, Tracheo])honjB ; the 

 Mesomyodi with tracheo-l)ronchial svrinx are often termed Oligomyodi, or Ilaploophona?, 

 though the latter name was originally intended for a more restricted group. The 

 terminology is somewhat intricate, but it is important that one who wishes to stuily 

 or understand the modern schemes of Passerine classification should master it thoroughly, 

 hence Fig. 229 is given to indicate the difference between the acromyodian and the 



