272 FACULTIES OF BIRDS. 
tumn, although in external appearance the young 
goose resembles the parent, no trace of aircells 
can be discovered in its bones, the interior of the 
bones being then filled with marrow. About the 
fifth or sixth month the marrow begins to disap- 
pear. This circumstance, which applies also to 
other birds, shows with what caution one should 
form an opinion, from young birds only, on the 
size of the aircelis. In many kinds of birds the 
aircells of some bones are nearly fully developed, 
although they have the openings of the bones which 
lead to the aircells.”* 
Not only the bones, but the quills of the feathers 
also make a part of this contrivance. These, while 
growing, are filled with an organized pulp; but as 
soon as they arrive at their full growth, this pulp, 
being absorbed, renders them light, and the lightness 
is increased by air from the atmosphere being in- 
_ troduced into their cavity through a small opening 
at the termination of the furrow where the quill or 
barrel ends and the plumelets of the feather begin. 
Air is also introduced in a similar manner into the 
plumeiets themselves. 
“Tn a journey,” says M. Tachard, “which we 
made to the loadstone mine, M. de la Marre wound- 
ed one of these large birds which our people cal] 
Grand Gosier, and the Siamese Noktho.... Its 
spread wings measured seven feet and a half. On 
dissection we found, under the fleshy panicles, very 
delicate membranes, which enveloped the whole 
body, which, folding differently, formed many con- 
siderable pouches, particularly between the thighs 
and the belly; between the wings and the ribs, and 
under the craw, some were so wide as to admit the 
two fingers ; these great pouches divided into many 
little ducts, which, by perpetual subdivision, ran into 
an endless multitude of ramifications, which were 
* Blumenbach, Comp. Anat., § 182. 
