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The retina and the pigment epithelium of the human eye contain sources of bioelectric currents, which give rise to intra- and extraocular electric current densities. This paper first gives a review on the magnetic fields arising from ocular currents: the magneto-oculogram (MOG) and the magnetoretinogram (MRG). A mathematical model is presented for calculation of the field distributions and a comparison with experimental data is made. Finally results from experiments on motion and light induced changes in ocular magnetic fields are used to determine retinal current densities.

The response of a magnetic gradiometer to various types of magnetic sources is analyzed. Both semiquantitative and quantitative methods for determining the noise immunity and the spatial sensitivity of the gradiometer are presented. A new class of magnetic gradiometers with unidirectional properties is introduced.

SAVAINEN, A. Magnetic measurements of pulmonary contamination. Scand. j. work environ. & health 4 (1976) 232-239. The magnetic determination of pulmonary contamination is based on the remanent magnetization of ferromagnetic contaminating particles. The remanent field of the externally magnetized particles is proportional to their amount and shows their distribution. Although only magnetizable particles are detected with this method, the amount of the inhaled ferromagnetic substance can be used when the total dust exposure of the worker is estimated. In this work five shipyard welders were studied. First the particles disposed to the lungs were externally magnetized and then their distribution was mapped with a sensitive magnetometer. The magnitudes of the remanent fields measured from the welders differed from the fields measured from controls by several orders of magnitude. The radiographic findings showed a good correlation with the magnetic measurements, and further experiments will prove whether this method can partly replace presently used radiological investigations.

In magnetocardiography (MCG) the magnetic field, produced by the electrical activity of the heart, is measured. This paper presents the preliminary results of the human fetal magnetocardiography (FMCG). The MCG of an adult heart was first recorded by BAULE and McFEE [1]. Recently, several research groups have utilized the superconducting quantum interference device (Squiü) in recording the MCG of the human heart [2,4,5]. Some of the MCG complexes are of high quality. The configuration of the complexes resembles the ECG but gives additional Information about the electrical activity of the heart in various diseases [4].