1. Some theoretical aspects of alveolar ventilation are
discussed, and an hypothesis presented which ascribes to a
common cause the increase in physiological dead space resulting from exercise, voluntary hyperventilation and abnormal
2. A method is described by means of which ventilatory
efficiency may be assessed during exercise. Its limitations
are enumerated and discussed.
3. Ventilatory efficiency has been studied during exercise
in healthy University students and old men. The results
are presented and appraised.
4. Possible clinical applications are briefly mentioned.