EXTERNAL PARTS OF BIRDS.— TOPOGRAPHY. 93 
turn) enveloped in muscle, along which in front lie the gullet (Lat. esophagus) and windpipe 
(Lat. trachea), with associate blood-vessels, nerves, ete. 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 hand of a bird, the neck is extremely flexible, to permit the neces- 
sarily 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 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 § or italic f, the lower belly of the curve, convex forward, fitting in between the 
forks of the merry-thought (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 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 Galline), in 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 cervical vertebra) with the skull, and behind at the first vertebra which bears free 
jointed ribs reaching the sternum. (See also p. 1383, 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 vertebre, 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-feathers themselves being beyond it; 
behind and laterally, it includes more or less of the legs, for these are generally buried in the 
common 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 scapular-arch, namely, the shoulder-blades (Lat. scapula), the coracoids, and the collar-bones 
(Lat. clavicula), all three of which come together at the shoulder-joint. The thoracic cavity 
is not separated by any partition or diaphragm from 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 vertebre (dorso-lumbar, sacral proper, and 
urosacral, as become immovably joined to one another, and laterally of the confluent haunch- 
