1864.] DR. £. CRISP ON THE ANATOMY OF THE SCREAMER. 15 
examined—the Gannet, Pelican, and Adjutant—have very light and 
airy skeletons. 
As I have said on a former occasion, the body of a bird, as regards 
a part of its mechanism, is not unlike a balloon. When the Gannet 
and the Pelican descend with the rapidity of an arrow upon a shoal 
of fish, which their quick sight enables them to see at a great dis- 
tance, the abdominal and thoracic air-cells are compressed by the 
abdominal and other muscles, and the greater part of the air is thus 
expelled and the bird descends with greater rapidity. The bird in 
question (Chauna chavaria) is no doubt one of rapid flight ; but pro- 
bably the great benefit it derives from the presence of air in its bones 
and under its skin is to enable it to walk with greater facility upon 
the aquatic plants, and thus obtain its food, which probably in a state 
of nature consists chiefly of Mollusca, judging from the form of its 
intestinal tube. 
The visceral anatomy of this bird presents some points of especial 
interest, and, judging from the reference to my notes of the dis- 
sections of a great many birds (British and foreign), there are some 
peculiarities in its organization that I have not before met with. 
The tongue is fleshy, thick, and rather pointed. The trachea is large 
above and small below; but the greater part of the tube is uniform 
in size, and the rings firm and unyielding ; the rings number 129. 
Two pairs of muscles are present at the lower part—the sterno- 
tracheales and broncho-tracheales; these are of large size. The 
eyes are large; irides of a light yellow colour. The lungs, heart, 
kidneys, thyroids, spleen, pancreas, generative organs, and renal 
bodies present no remarkable deviation from the ordinary type, ex- 
cept that the generative organs and renal bodies are of a deep orange 
colour. The lobes of the liver (in both specimens) are connected by 
a very small, narrow isthmus, much smaller than I have seen it in 
any other bird of the same size. But the intestinal tube of this 
bird, as shown by the drawings on the table, offers some of the most 
cutious anomalies. The cesophagus is of uniform size and of mode- 
rate capacity ; the proventriculus thick and capacious; the glands 
large and flask-shaped ; the gizzard thin, its parietes of nearly the 
same thickness in every part; the calibre of the small intestines 
moderate, that of the rectum very large. The mucous lining of this 
gut forms forty-two transverse folds, so as to extend greatly the 
absorbing surface. The subjoined is the length of the canal :— 
inches. 
ALDISLT ES gal ape near ee ra 12 
GAPE cers esc cti es end Rice <a ho epee 
pil MtESHINER. Ow te oe ee Ap! 
Mpipentices, three)... ..% 0. cit ae 
Large intestine ...... Anse Peas 13 
833 
The intestinal tube holds 14 ozs. 3 drachms of water. The appen- 
dices, although short, are very capacious, and, like the large intes- 
