8 
i 
GUIDE TO THE 
arriving about June and departing to its breeding haunts 
about the middle of October. It is a- curious-looking 
bird, owing to its huge bill, nearly bald head, bare neck, 
grey stony eyes, and long pendular pouch. Its body is 
of a nearly uniform grey colour, and it has long stilt-like 
legs. Its most remarkable structural peculiarity is its 
pouch, which has no connection whatever with its digestive 
system, but is only a receptacle for air which it receives 
from two crescentic, valvular orifices that occur in the 
nasal passage a little behind the opening of the nostrils. 
These communicate with a large chamber in which the 
orbit is situated, there being a great cavity immediately 
below the eye of the bird, which is suspended in it, and 
another large cavity occurs farther back in which all the 
muscles are seen free as in the anterior cavity; and a single 
orifice below the mesial line of the base of the skull com¬ 
municates with the neck or gular pouch. The pouch in 
reality consists of two, but the one on the right side, 
like the asymmetry that prevails in the generative organs 
of birds, is nearly suppressed, the left pouch being the 
one that is so largely developed. The right pouch is 
indicated by a small flaccid cavity separated from that 
of the left side by a longitudinal septum of delicate con¬ 
sistence. The pouch does not communicate with the 
lungs, but the whole of its inner surface is highly vascular 
and its walls are endowed with remarkable contractility. 
Long after death the pouch may be distended to a great 
degree, and when the tension is taken off it, at once con¬ 
tracts into numerous folds. This pouch has doubtless 
some relation to the mechanism of flight and to the aera- 
ation of the blood, both of which functions are intimately 
related to each other in birds as is well known, and it 
