umbilication

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

It is pea-sized and globular in shape; its umbilication has been usually quite removed by the complete filling of its chamber with distinctly purulent contents; it is often surrounded by a halo due to hyper�mia or exudation; and, the total number of individual lesions being then fairly determined, it is often closely set against its fellows, islets of unaffected integument having meantime become fewer and more contracted.

This is sometimes termed a secondary 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.

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