A NEW DARK ADAPTATION TESTER

A New Instrument for Dark Adaptation Tests.

A New Grain Hardness Tester

.\ hardness tester, especially adapted for grain, was cor~structecl by modifying a commercial portable soft metal tester known as the Barcol Impressor. h preloaded stylus is forced into grain sections preparetl by rneans ot a microtome. The displacement of the stylus, nleasured by a dial micrometer, is used as a hardness index. This has been related to tlie l'ickers tlianlontl pyramid hardness ...

Light and dark adaptation.

The high-frequency cutoff of the semicircular canals is unknown but probably also lies above 5 Hz. The high-frequency cutoff of the extraocular muscles is 1 Hz. so that central mechanisms (that introduce phase lead) must compensate from 1 to 5 Hz. The pursuit system begins to cut off between 0.5 to 1 Hz. so that it can compensate for slow head movements while the vestibular system compensates f...

Aging and dark adaptation

Older adults have serious difficulty seeing under low illumination and at night, even in the absence of ocular disease. Optical changes in the aged eye, such as pupillary miosis and increased lens density, cannot account for the severity of this problem, and little is known about its neural basis. Dark adaptation functions were measured on 94 adults ranging in age from the 20s to the 80s to ass...

Dark Adaptation in Dineutes

The level of dark adaptation of the whirligig beetle can be measured in terms of the threshold intensity calling forth a response. The course of dark adaptation was determined at levels of light adaptation of 6.5, 91.6, and 6100 foot-candles. All data can be fitted by the same curve. This indicates that dark adaptation follows parts of the same course irrespective of the level of light adaptati...