1904-5.] Action of Radium Bromide on Eyeball of Frog. 839 
the radium was removed the light from the overhead electric 
lamps gave the usual phenomena, namely, a rise of from 5 to 8 divs. 
when light on, and a rise of 4 to 6 divs. when light off. 
We next examined the fluorescing properties of the specimen 
of radium in our possession. This was done with the aid of a 
blackened box 43 cm. long, by 27 cm. broad, and 36 cm. in height. 
There was a hole in the end of the box, and when the box was 
inverted on the table, and a cloth was placed over the observer’s 
head when he looked through the hole (as in focussing a camera), 
there was total darkness. Various minerals and fluids were placed 
before the radium, and fluorescence was observed. One substance 
in particular, willemite (zinc ortho-silicate), gave beautiful results. 
The radium was placed within two pill boxes, with the radium 
facing the bottom ; the bottom of the pill box was covered with 
black paper, and a bit of thin aluminium was also interposed, but 
still fluorescence, although faint, could be observed. When the 
pill box was directed to the eye of the observer, with the coverings 
before mentioned, it appeared to be absolutely black, that is to 
say, no rays emerged which acted on the eye of the observer. 
The interposition of a lead plate produced absolute blackness. 
When the pill box was reversed so that the bottom of the leaden 
capsule was towards the observer’s eye, there was absolute darkness. 
Expt. 4. A sheep’s eye fresh was placed in the dark chamber, with the 
radium opposite. No fluorescence of the cornea was observed. The 
anterior segment of the eyeball was cut off, leaving the lens and the 
vitreous tumour ; no fluorescence. The lens alone gave no fluorescence. The 
vitreous was evacuated without injuring the retina ; no fluorescence. Finally 
the vitreous and retina were removed so as to expose the brightly shining 
sclerotic ; this showed no fluorescence. The eyeball of a large frog was 
examined in the same way with negative results. The lenses of several 
eyes were examined, but no fluorescence was observed. 
It would appear, therefore, that none of the structures of the 
eyeball are fluorescent, and that the action of radium in the retina 
cannot arise from light so produced. 
Expt. 5. The willemite that fluoresced with radium was now placed in the 
black box between the electrodes ; an eyeball was so placed on the pads that 
its cornea was directed downwards towards the fluorescing mineral ; and the 
radium holder was so adjusted that the radium was directed past the side of 
the eyeball, downwards towards the fluorescing mineral. On looking into 
the little box with a cloth over the head the mineral was seen to be 
fluorescent. The lead plate could be interposed between the radium and 
the fluorescent surface. 
