EXTERNAL PARTS OF BIRDS. — TOPOGRAPHY. 93 



turn) onvoloped in muscle, along which in front lie the gullet (Lat. oesophagus) and windpipe 

 (Lat. trachea), 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 hill, which is the true hand of a bird, the neck is extremely flexible, to permit the neces- 

 sarilv 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 some- 

 times exceeds that of the body and taU. 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 itaUc /, the lower belly of the curve, convex forward, fitting in between the 

 forks of the merry-thought (Lat. furculiim), 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 mechan- 

 ical 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 generalization, 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 Insessores ; intermediate in swimming birds. But many swimmers, as 

 swans and cormorants, have extremely long necks ; and some waders, as plovers, have very 

 short ones. A long neck is a rarity among the higher birds (above the Gallince),'m most of 

 which the head seems to nestle upon the shoulders. The longer the neck, the more sinuous 

 and flexible is it likely to be. Anatomically, the neck ends before at the articulation of the 

 atlas (first cer\dcal vertebra) with the skull, and behind at the first vertebra wliich bears free 

 jointed ribs reaching the sternum. (See also p. 183, Anatomy.) The shape of the 



Body proper, or Trunk, is obviously referable to that of the egg ; it is ovate (Lat. 

 ovum, an egg; whence oval, the plane figure represented by the middle lengthwise section of 

 an egg; ovate or ovoid, the solid figure). The swelling of the breast represents the greatest 

 diameter of the egg, usually near the larger end. But the ovoid is never perfectly expressed, 

 and departures from the figure are numberless. In general, the higher perching birds have the 

 body nearly of the ovate shape ; among waders, the figure is usually compressed, or flattened 

 vertically, as is well seen in the herons, and still better in the rails, where the lateral narrow- 

 ing is at an extreme ; among swimmers, the body is always more or less depressed, or flattened 

 horizontally, and especially underneath, that the birds may rest on the water with more 

 stability, as well shown by a duck or diver. Anatomically the body begins with the foremost 

 dorsal vertebree, or those that bear true ribs ; laterally, it ceases quite definitely at the shoulder- 

 joints, the whole of the fore limb being outside the general content of the trunk; behind, in 

 the middle line, it includes everything, only the tail-featliers themselves being beyond it ; 

 behind and laterally, it includes more or less of the legs, for these are generally buried in the 

 coTnmon integument of the body to the knee-joint, nearly or quite so, and sometimes to the 

 heel-joint ; though more strictly the trunk should be limited by the hip-joint. The rib-bearing 

 part of the back-bone, the ribs themselves, and the greatly enlarged breast-bone (Lat. sternum) 

 compose the cavity of the chest (Lat. thorax). Upon this bony box, which contains the 

 heart and lungs and some other viscera, are saddled on each side the bones of the shoulder-girdle 

 or scapiular-arch, namely, the shoulder-blades (Lat. scapida) ,i\\e coracoids, and the collar-bones 

 (Lat. clavicula), aU three of which come together at the shoulder-joint. The thoracic cavity 

 is not separated by any partition or diaj)hragm fi-om that of the belly (Lat. abdomen), which 

 with the pelvis, or basin, contains the digestive, urinary, and genital organs. The pelvis is 

 composed, in dorsal mid-line, of so many of the vertebrfe (dor so-lumbar, sacral proper, and 

 urosacrnl, as become immovably joined to one another, and laterally of the confluent haunch- 



