136 GENERAL ORNITHOLOGY part ii 



skull of owls is such, that the eyes are directed forward, and such 

 birds are said to have " eyes anterior." Owls also have enormous 

 outer ears, in some cases provided with a movable flap or conch, 

 closing upon the opening like the lid of a box ; in many cases the 

 ear-parts, and some of the cranium itself, being unsymmetrical. In 

 most birds the ear-opening is quite small, and only covered by 

 modified feathers, the ear-coverts or auriculars. In the woodcock 

 and snipe, owing to the way the brain-box is tilted up, the ears are 

 below and not behind the eyes. The mouth (Lat. os, gen. oris) is 

 always a fissure across the front of the head. The cleavage varies, 

 both in extent and direction ; the latter is usually horizontal, or 

 nearly so, but may trend much downward ; the former varies from 

 a minimum, in which the cleft does not reach back of the homy 

 part of the bill, as in a snipe, to the maximum seen in fissure-bUled 

 birds like the swifts and goatsuckers, which gape almost from ear 

 to ear. There are no other openings in the head proper, for the 

 nostrils are always in the bill. The 



Neek, in effect, is a simple cylinder, rendered somewhat hour- 

 glass-shaped, as above said. It consists of a movable chain of 

 bones, the cervical veriebrce (Lat. cervix, the neck ; verto, I turn) 

 enveloped in muscle, along which in front lie the gullet (Lat. 

 (esophagus) and windpipe (Lat. traeliea), with associate blood-vessels, 

 nerves, etc. Its length is very variable, as is the number of its 

 bones, the latter ranging from 8 to about 26. Bearing as it does 

 the head, with the bill, which is the true haiid of a bird, the neck 

 is extremely flexible, to permit the necessarily varied movements 

 of this handy member. Its least length may be said to be that 

 which allows the point of a bird's beak to reach the oil-gland on 

 the rump ; its greatest length sometimes exceeds that of the body 

 and tail together, as in the case of a swan, crane, or heron. The 

 length is usually in direct proportion to that of the legs, in obvious 

 design of allowing the beak to touch the ground easily to pick up 

 food. The neck is habitually carried in a double curve, like an 

 open S or italic/, the lower belly of the curve, convex forward, 

 fitting in between the forks of the merrythought (Lat. furculum), 

 the upper curve holding the head horizontal at the same time. 

 This " sigmoid flexure " (sigma, Greek S), highly characteristic of 

 the bird's neck, is produced by the saddle-shaping of the articular 

 surfaces of the several bones. The mechanical arrangement is such, 

 that the sigma may be easily bent till the upper end (head) rests on 

 the lower convexity, or as easily straightened to a right line ; but 

 little if any further deviation in opposite curvature is permitted. 

 As a generalisation, the neck may be called relatively longest in 

 wading birds, as herons, cranes, ibises, etc. ; shortest in perching 

 birds, as the great majority of small Passeres ; intermediate in 



