752 VERHOEFF AND BELL. 



only waves greater than 0.295 microns in length to pass *. As will 

 be seen, however, this procedure was unsuccessful. No germicidal 

 effect on bacteria within the cornea could be noted even when exposures 

 through this screen were used which were sufficient to produce severe 

 keratitis and even injiu-e the epithelium of the lens capsule. 



As light sources in the following experiments the magnetite arc and 

 the quartz mercury-vapor lamp were chiefly used. To obviate the 

 remote possibility that the cadmium-zinc arc employed by Hertel 

 might possess some special advantage, this arc was also used. That 

 greater intensity was obtained with our cadmium-zinc arc and quartz 

 lens than was obtained by Hertel is proved by the fact that not only 

 severe keratitis but also marked changes in the epithelium of the lens 

 capsule were produced. 



The mercury-vapor lamp used was the Cooper-Hewitt model with- 

 out the globe (220 volts, 3.5 amperes). 



The magnetite arc was of the ordinary self-regulating type as known 

 to trade, without the globe. The voltage was about 80, the amperage 

 from 9.8 to 10. The light was passed through a quartz water-cell 

 5 cm. in thickness, and concentrated on the cornea by means of a 

 quartz lens 4 cm. in diameter and 9 cm. in focal length, placed 20 cm. 

 from the light source. In Experiments 6 and 7 still greater intensity 

 was obtained by means of a second quartz lens 23 mm. in diameter 

 and 15 mm. in focal length. 



In the case of the cadmium-zinc arc, the same apparatus was used 

 except that the electrode consisted of an alloy of equal parts of cad- 

 mium and zinc in a thin-walled copper cylinder, and was water-cooled. 

 The water-cell was omitted. The voltage was about 80, the amperage 

 about 6.8. 



A number of experiments were first made by injecting staphylo- 

 cocci or pneumococci into the corneas of rabbits and after twenty-four 

 hours exposing the resulting abscesses to the ultraviolet light. Healing 

 did not seem to be hastened, but since recovery ultimately occurred, 

 as it did also in the control eyes, these experiments are not regarded 

 as sufficiently conclusive and are not given in detail. Experiment 1, 

 however, in which tubercle bacilli were injected into the cornea, was 



4 Since this wave-length has been found to be the hmit of transparency for 

 the cornea, it would be expected that such a screen would protect the cornea 

 from injury, the longer waves not being absorbed by the latter. As a matter 

 of fact I have found that it does almost completely protect the corneal stroma, 

 but permits severe injury or destruction of the epithelium, corneal corpuscles 

 and endothelium. 



