30 
TEANS ACTIONS OF THE TEXAS ACADEMY OF SCIENCE. 
cut out of cardboard as shadows against the tube.” Dr. Bell seems to 
think that rays other than the X-rays were effective in exciting vision, 
since cardboard, which is highly transparent to X-rays, should not have 
stopped the vision if it were the X-rays which excited it. If Dr. Bell’s 
interpretation of his results is correct, they have great scientific interest 
as indicating the complex nature of the radiation, so little understood, 
to which a Crooke’s tube gives rise. Dr. A. E. Kennedy, in the transac- 
tions of the American Institute of Electrical Engineers, December, 1896, 
says that he has made some experiments upon the perception by the blind 
of the X-rays. He thinks his “experiments seem to show that when the 
mechanism of the retina has been destroyed, leaving the optic nerve in a 
useless or atrophic condition, no X-rays are perceived. When the mech- 
anism of the eye is intact, but the optic nerve is deranged or paralyzed, 
some visual conception may be obtained by the stimulus of X-rays. 
When the optic nerve and the retina are both intact, but the cornea is 
deranged, the fluorescent effect of X-rays upon a calcium tungstate screen 
held before the eyes excites the visual sensation in the ordinary manner to 
a large degree that depends upon the corneal opacity. It would seem, 
however, although it is not certain, that the corneal opacity may itself 
feebly serve as a fluorescent screen, and the X-rays filtered through wood 
or pasteboard, falling on some eyes that are corneally blind, produce a 
faint visual sensation of diffused light.” 
The outfit employed in our test is of the best. A double focus tube is 
excited by a Tesla coil, capable of giving an eight-inch discharge. The 
X-rays produced will show a shadow of the hand upon the fluorescent 
screen at a distance of twenty-five or thirty feet. 
Altogether, eleven subjects were experimented upon. One of these is a 
student in the University of Texas, and being highly intelligent and sci- 
entifically trained, was able to analyze and to accurately record his sen- 
sations. Of the subjects treated, seven had no light perception, the blind- 
ness being due, principally, to affection of the optic nerve, and four had 
some light perception. Three of the four having light perception were 
blind from trouble with the cornea and lens, while the fourth had pa- 
ralysis of the optic nerve. The four having light perception were able to 
obtain a sensation of the light from the arc light placed at a distance of 
three or four feet. It is not necessary to enter into details regarding the 
test made upon each subject, for the tests were practically identical in 
each case, and the results the same for all. The manner of experimenting 
was, first, to allow the subjects to look directly at the tube at a distance 
from it of about one foot, and to inquire if they thought they had any 
light perception. In several cases of total blindness the subject seemed 
to think he or she had a light perception when the X-rays were excited 
in the tube; but, as further experiments proved, they were in all cases 
mistaken, and the supposed light perception must have been due to the 
