Page:Popular Science Monthly Volume 91.djvu/728

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Jennings' Self-Recording Color Test

A perforated cardboard ex- hibiting confusion colors is placed before the applicant, one perforation corresponding with each color and shade. Some shade of red or green is placed in front of the applicant and he is asked to name it and to select by punching through the perforations anything in the chart which contains - red or green, as the case may be. These punches are recorded on a blank beneath the chart so arranged as to show whether or not they were punched correctly

��Testing the Muscle Balance of the Eye

The muscle balance of the eye must be in perfect alinement. In other words, there must be no latent tendency for the eye to turn up or down or in or out. If there is, the aviator may see double and thus endanger his life at a critical moment

��Popular Science Monthly

���The Effect of the Different Head Positions

The position thirty degrees forward for purposes of whirling tests, brings the horizontal or external canal of the ear into the plane of the turning. This is the position used for the routine examinations for nys- tagmus and pass-pointing. Nystagmus is the term used to designate the visual disturbance set up by the whirling. It may be described as a rhythmic to and fro motion of the eyes con- sisting of two specific move- ments — a slow movement in one direction, followed immediately by a rapid movement in the opposite direction. This con- dition lasts only so long as the fluid within the canal tested continues to flow artificially. Placing the head ninety degrees forward would have the same effect upon this external canal as a superior canal running directly from ear to ear

���(Compton-Johnson Co.)

��The Sixth Sense, the Sense of Balance, Lies in the Labyrinth of the Internal Ear The internal ear or labyrinth consists of a bony and a membranous part, the latter contained in the former. The bony labyrinth is composed of the vestibule, the semi-circular canals and the cochlea. These three canals constitute what is known as the static labyrinth upon which we depend for our sense of balance. The bony canals contain the membranous canal, and the membranous canal, in turn, contains the endolymph, which is a fluid that fills the mem- branous canal. The flowing of the endolymph in the semicircular canals is absolutely essential to man's normal station in space with eyes closed or in any situation in which he cannot judge his position by sight. Without a perfect labyrinth, a man could not fly safely for the simple reason that he would have no sense of balance

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