These "bristles" are more thickly set in young birds, but become thinner with age, until they almost totally disappear--leaving both head and neck quite naked.
This peculiarity causes a resemblance between the adjutant bird and the vultures; but indeed there are many other points of similarity; and the stork may in all respects be regarded as a vulture--the vulture of the _grallatores_, or waders.
In addition to the naked neck, the adjutant is furnished with an immense dew-lap, or pouch which hangs down upon its breast--often more than a foot in length, and changing from pale flesh colour to bright red, along with the skin of the throat.

At the back of the neck is found still another singular apparatus--the use of which has not been determined by the naturalist.

It is a sort of vesicular appendage, capable of being inflated with air; and supposed to serve as an atmospheric buoy to assist in sustaining the bird in its flight.

The inflation has been observed to take place under exposure to a hot sun; and, therefore, it is natural to infer, that the rarefaction of the air has something to do in causing [the bird to use this organ].

As the adjutant often flies to a great height, it is possible that this balloon-like apparatus is necessary to sustaining it in the rarefied atmosphere found at such an elevation.