THE magnetic field of the human heart was first recorded some 30 years ago. This early magnetocardiogram was measured using a cumbersome apparatus with two large induction coils, each of which had about two million windings. In contrast, Meinhard Schilling and co-workers at the University of Hamburg in Germany have now demonstrated a portable instrument that can detect very weak biomagnetic signals (Appl. Phys. Lett. 69 2751).
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