Probic vent

The Probic Vent was a part of Sontaran anatomy, in the form of a small metallic tube attached to the back of the Sontaran's neck. This Probic Vent was normally used by the Sontarans as a feeding tube during space or time-flight. The Vent was also a major weakness, since a blow to the Probic Vent could knock a Sontaran unconscious or even kill them. The Sontarans didn'r find it a problem, however, since it meant that they must always face their enemy.