WINTER CRASHES.
“In the ‘nystagmus test’ the applicant is first spun in the chair exactly ten times in twenty seconds, accurately checked with a stop watch. The examiner now carefully observes certain lateral, jerking movements of the eyes which normally appear, but should cease on an average in twenty-six seconds. A certain variation is allowed from the normal time, and cadets for pilots not conforming to this test should not be allowed to fly. In it the head is tilted forward to an angle of thirty degrees in order to stimulate only those canals which lie in the horizontal plane.
“In order to stimulate those canals lying in the vertical plane, ‘falling tests’ are employed. The subject is instructed to lean forward, resting his forehead on his hands which are placed on his knees, and is then turned alternately to right and left five times in ten seconds.
“Should he be rotated to the right and be ordered to sit up, he should immediately fall to the right, which is the normal reaction, but should he sit directly upright or fall to the opposite direction, a faulty functioning of these canals or of the pathways in the brain is thus demonstrated.
“‘Pointing tests’ are applied somewhat similarly. The candidate is turned ten times in ten seconds alternately to right and left, with eyes closed. He is then instructed to raise his arm and point to a fixed object, usually the examiner’s finger, of the position of which he is already aware. As a result of the dizziness produced, if he has been turned to the right, he should point to the right of the object. This ‘past-pointing’ is a normal reaction, and any considerable deviation will immediately reject the applicant. Even after the chair has stopped, the man still feels that he is turning and is endeavouring to locate the fixed point. The ‘past-pointing’ shows that he is attempting to allow or the rotary motion which he is still experiencing, though actually the chair is stationary.
“Since the more sensitive, theoretically, a man is, as shown by ‘turning tests,’ the more likely he is to be a good pilot, as he should be able to detect more accurately and early the movements of his plane without the use of his eyes. This is, however, true only to a limited degree, for we have found that as a rule the higher the nystagmus time, the more likely is the man to suffer from vertigo, nausea or vomiting in the air. On the other hand, theoretically, a man with a short period of nystagmus should be less sensitive to unpleasant, subjective sensations, and those with ‘dead labyrinths’ ought to be immune.
“The practical deduction is that in good pilots the ocular oscillations must not vary to any considerable extent, say not more than ten to twelve seconds; on the other hand the lower or shorter the time the better a man should be able to stand the violent swaying of a captive balloon, since it is this motion above all others that produces the most intense nausea and emesis. Following the above to its logical conclusion, we in practice reject men who show too high a nystagmus time, and recommend for observers, and especially for balloonists, those showing sluggish reactions.”