Photo's description:

SUIT CHECK - Project Mercury pressure suit specialist Joe. W. Schidt adjusts a respirometer attached to the helmet of astronaut Virgil I. Grissom during a dress rehearsal for the National Aeronautics and Space Administration's second manned suborbital flight planned for the week of July 16. Respirometer enables ground medical personnel to monitor the pilot's breathing rate during the countdown and flight. Hose attached to the left side of the pilot's suit brings breathing oxygen into the suit. Expelled oxygen is then vented out a port on the side of the helmet and passed through an air conditioning system beneath the astronaut's couch where it is purified before being recycled into the suit. Gauge on left arm indicates pressure within the suit. Canon plug on the right thigh brings medical information out of the suit for telemetering to ground stations. Suit is not inflated during the mission unless there is a failure in cabin pressure, in which event the "V" shaped cable around the neck ring is adjusted prior to flight to prevent helmet from rising should it be necessary to pressurize the suit.