756 VERHOEFF AND BELL. 



CONCLUSIONS. 



The results of these experiments prove conclusively that ultraviolet 

 light cannot under any conditions destroy bacteria within the cornea, 

 even when the latter is perfectly transparent, without at the same time 

 severely injuring the corneal tissue. Destruction of bacteria within 

 the transparent cornea was obtained only when a light intensity and 

 exposure were employed sufficient to cause complete destruction of 

 the corneal corpuscles and intense injury to the corneal lamellae 

 (Experiment 6). 



Moreover, it does not seem possible that ultraviolet light could in 

 practice be successfully used to destroy bacteria within a corneal 

 abscess or ulcer, that is, when the cornea was no longer clear, even 

 with the sacrifice of corneal tissue, as in the case of the actual cautery. 

 For either the exposures would have to be impracticably prolonged, 

 or such extreme intensity of light would be required that the heating 

 effect would exceed that of the abiotic action. It is doubtful also if 

 ultraviolet light of such intensity could be made available for thera- 

 peutic purposes. 



It must be concluded, therefore, that so far as direct destruction 

 of bacteria within any of the tissues of the body is concerned, ultra- 

 violet light possesses no therapeutic value. 



GENERAL CONCLUSIONS. 



1. The liminal exposure capable of producing photophthalmia to 

 the extent of conjunctivitis accompanied by stippling of the cornea, 

 is in terms of energy about 2 X 10^ erg seconds per square cm. of 

 abiotic radiation of the character derived, for example, from the quartz 

 lamp or the magnetite arc. About two and a half times this exposure, 

 i. e., 5 X 10^ erg seconds per square cm. is required to produce loss 

 of corneal epithelium. 



3. The abiotic action of the cornea and conjunctiva produced by 

 any radiating sources follows the law of inverse squares and is directly 

 proportional to the total abiotic energy received. It can therefore 

 be definitely predicted from the physical properties of the source. 



3. After exposure of the eye to abiotic radiations there is a latent 



