146 Memory as an Aid to Vision
ber a period while they were looking at them, but could not remember even their own names.
Patients may measure the accuracy of their memory of the period, not only by comparing it with the sight, but by the following tests:
When the memory of the period is perfect it is instan taneous. If a few seconds or longer are necessary to obtain the memory, it is never perfect.
A perfect memory is not only instantaneous, but con tinuous.
When the period is remembered perfectly perfect sight comes instantaneously. If good vision is obtained only after a second or two, it can always be demonstrated that the memory of the period is imperfect and the sight also.
The memory of a period is a test of relaxation. It is the evidence by which the patient knows that his eyes and mind are at rest. It may be compared to the steam-gauge of an engine, which has nothing to do with the machinery, but is of great importance in giving infor mation as to the ability of the mechanism to do its work. When the period is black one knows that the engine of the eye is in good working order. When the period fades, or is lost, one knows that it is out of order, until a cure is effected. Then one does not need a period, or any other aid to vision, just as the engineer does not need a steam-gauge when the engine is going properly. One patient who had gained telescopic and microscopic vision by the methods presented in this book said, in answer to an inquiry from some one interested in inves tigating the treatment of errors of refraction without glasses, that he had not only done nothing to prevent a relapse, but had even forgotten how he was cured.