umbilication

Empty cells becoming confluent, vesicular by incurvation of the circular margin, forming a deep and round umbilication.

The umbilication of the mature pock is doubtless due to the situation of such lesions at the orifices of the excretory ducts of the skin-glands.

Eventually, it too, as a result of the maceration and tension incidental to the complete filling of the pock with pus-elements, is ruptured or stretched, and the umbilication of the pustule disappears.

Umbilication rapidly occurs at the apex, and simultaneously their contents become lactescent and gradually sero-purulent.

Early in their career an apicial depression can be seen, which later deepens into a characteristic umbilication.