Barrett—On Entoptic Vision. 133 
of these moving corpuscles in the eye in various states of health 
and under the influence of alcohol and other drugs which hinder 
and destroy their activity. 
The subject of phosphenes, or the luminous impression produced 
by pressure on the eyeball, or other stimulation of the retina, and 
of after-images and of ocular spectra, are subjective Entoptic 
phenomena, which have been fully dealt with by writers on 
physiological optics, and into these I do not propose to enter. I 
have not, however, met with any reference by these authorities to 
some curious subjective entoptic phenomena, described by Sir 
John Herschel in a lecture, on “ Sensorial Vision,” delivered in 
1858, and published in his ‘‘ Familiar Lectures on Scientific 
Subjects.” Sir John states that, when the eyes were in complete 
darkness, he frequently saw covering the field of vision patterns of 
perfect symmetry and geometrical regularity, sometimes lozenge- 
shaped, but often passing into more complex forms of equal 
symmetry. He discusses how these geometrical spectra can 
originate, for they do not appear to be retinal impressions, or 
mental reminiscences; they do not arise from any conscious 
effort of the mind ; they recurred, in different shapes, just before 
Japsing into unconsciousness on two occasions when he was under 
chloroform ; and he suggests that they afford some evidence “ of 
a thought, an intelligence working within our own organization 
distinct from that of our own personality,”’! or, as psychologists 
would now say, they afford some evidence of a ‘“‘ sub-conscious 
self.” 
1 «Familiar Lectures on Scientific Subjects,’’ by Sir J. F. W. Herschel, Bart., 
K.H., D.C.L., F-R.S., &C., p. 412, 
