;wo zooLooY 



SECT. 



the thick covering of feathers, only the feet are to be seen in tlie 

 living Biixl, each covered with scales and terminating in four digits 

 {dfj. 1' — d(j.^'), three directed forwards and one backwards. 



In order to make a fair comparison of the outer form with tliat 

 of other Craniate types, it is necessary to remove the featliers. Wiien 

 this is done, the Bird is seen to have a long, cylindrical, and very 

 mobile neck, sharply separated both from head and trunk. The 

 true tail is a short, conical projection of the trunk, knowm as the 

 nropiff/ium, and giving origin to the group of large feathers (rd.) to 

 which the word " tail" is usually applied. On the dorsal surface 

 of the uropygium is a papilla bearing on its summit the opening 

 of a large gland, the oil-gland (o.gl^, the secretion of which is 

 used for lubricating or " preening " the feathers. 



The Avings show the three typical divisions of the fore-limb, 

 upper arm, fore-arm, and hand, but the parts of the hand are 

 closely bound together by skin, and onl}' three imperfectl3'^-marked 

 digits, the second (dg, .?) much larger than the first (dg. 1) and 

 third {dg. 3), can be distinguished. In the position of rest the 

 three divisions of the wing are bent upon one another in the form 

 of a Z ; during flight they are straightened out and extended so 

 that the axis of the entire wing is at rio-ht ansfles to that of the 

 trunk. On the anterior or preaxial border of the limb a fold of 

 skin stietches between the upper arm and the fore-arm ; this 

 is the (dar memhranc or 'jivc-iJatagium {irr. ijigm.). A similar but 

 much smaller fold extends, postaxially, between the proximal 

 portion of the upper arm and the trunk ; tliis is the j^ost-jjatagmm 

 llJt.ptgm.y 



In the hind-limb the short thigh is closely bound to the trunk, 

 not standmg well out as in a Reptile, but directed downwards and 

 forwards ; the long shank extends from the knee dowuAvards and 

 backwards ; and the foot is clearly divisible into a proximal portion, 

 the tarso-metatarms {ts. mtts.), and four digits, of which one, the 

 halkix (dg. 1'), is directed backwards, the others, the 2nd, 3rd, and 

 4th of tlie typical foot, forwards. The entire hind-limb is in a plane 

 jmrallel with the sagittal plane of the trunk. 



The mouth is terminal, and is guarded by the elongated upper 

 and lower beaks ; it has, therefore, a very Avide gape. On each 

 side of the base of the upper beak is a swollen area of soft skin, 

 tlie cere ((■)'.), surrounding the nostril (m«.), which has thus a remark- 

 ably backward i)osition. The eyes are very large, and each is 

 guarded by an upj^er and lower eyelid and a transparent nicti- 

 tating membrane {wt. m.). A short distance behind the eye is the 

 mcditorg (qicrturc (an. ap.), concealed by feathers in the entire 

 Bird, and leading into a short external auditory meatus, closed 

 below by the tympanic membrane. The anus or cloacal aperture 

 {an.) is a large, transversely-elongated aperture placed on the 

 ventral surface at the junction of the uropygium with the trunk. 



