field

Any definite circumscribed area, auditory f. That portion of the space surrounding the ear in every part of which a given sound is audible by the ear. The binaural auditory f. is that portion of space in which a given sound is audible when both ears are used, binocular f. of vision. That portion of space in which the f's of vision of the two eyes overlap, i. e., in which binocular vision is po ible, central f. of vision. See visual f. Cohnheim's f's. See' Cohnhevm's areas, under Cohnheim. deaf f's of the ear. Two small triangles, the first of which lies in front and above, the other behind and above the ear. A sonorous object, when entering either of these regions is heard much le distinctly than outside of them, direct f. of vision. See visual f. f. of a lens. The area from which rays coming to a lens are brought to a focus by the latter; the range of surface distinct through a lens. f. of a microscope. See /. of view. f. of audition. See auditory f. f. of fixation, f. of regard. See visual f. f. of view. The area visible through the microscope when it is in focus, f. of vision. See visual f. indirect f. of vision. See visual f. magnetic f. The range of influence of a magnet, unilateral f. of vision, uni ocular f. of vision. The visual f. taken for one eye only, visual field. The entire surface from which, at a given distance, light reaches the retina, the eye being fixed. The ordinary limits of the visual f. for white lights are, internally, 55 ° to 60 °; externally, 90 ° to 1000; upward, 550; downward, 60 °. The visual f. for colors is smaller than that for white light, that for blue having the widest limits, and for red the narrowest. The direct or central f. of vision comprises that part of the external world of which the projection falls on the fovea. The indirect or peripheral field comprises that part of which the projection falls on the retina outside the fovea.