LAST YEAR my co-workers and I reported in a preliminary study on the relation of cysteine treatment to x-ray damage of the rabbit's eye which had been exposed locally to a single dose of 1,500 r of penetrating x-rays. There was at this time strongly suggestive evidence that among the signs of radiation damage to the eye two characteristic late effects of such radiation, epilation and x-ray cataract, were partially prevented by the intravenous use of 2 gm. of cysteine prior to irradiation.
These animals have been followed now over periods of 12 to 16 months. Total cataract has developed in the control group in 12 of 14 animals within the observation time of 14 months. None of the cysteine-pretreated eyes showed at this time a lenticular opacity which was dense enough or extensive enough to interfere substantially with the visibility of fundus details. However, all these lenses exhibited some