Von Bally [10] discusses the relative merits of holography at the tip and at the eyepiece of the endoscope and describes the adaptation of an otoscope for making both single-exposure holograms and holographic interferograms of the eardrum. Brown et al. [11] describe an investigation into the human cardiac cycle using double-pulse interferograms of the chest and neck region, a fairly complicated operation. As the interval between pulses is much shorter than a single cardiac cycle, a large number of double pulses were necessary, triggered by the R-wave peak on the electrocardiogram, with delays of various fractions of a complete cycle. e ambiguity of direction of movement was resolved by rotating the reference mirror approximately 6 μrad between exposures (see p. 467).