EFFECTS OF RADIANT ENERGY ON THE EYE. 675 



that contain two nuclei of nearly equal size always contain smaller 

 buds in addition. At first glance the nuclear buds may be mistaken 

 for persisting basophilic granules, but careful examination shows that 

 they bear no relation to the latter either in appearance or origin. 

 Few if any mitotic figures can now be seen in the exposed area or else- 

 where. 



At the end of 5 weeks or 2 months the capsule shows about the 

 same appearances as after 10 days (PI. 3, Fig. 7) . There is perhaps still 

 greater variation in the sizes of the nuclei, and a greater number of the 

 excessively large ones. The cells with double nuclei and nuclear buds 

 are still present. In case of the extremely severe exposures, a few 

 cells are found still containing basophilic granules after two months. 



In connection with the foregoing observations on the lens capsule 

 several interesting questions arise. In the first place how is the abun- 

 dant mitotic division of the unexposed cells in and around the wall to 

 be explained? This proliferation is not due to minimal exposure to 

 the rays for it does not occur in the pupillary area 48 hours after 

 liminal or subliminal exposures. It is also not due to heat trans- 

 mitted by the iris, because when a flint screen is substituted for a 

 crown screen it does not occur after exposures more than four times 

 as long. The only remaining possibility seems to be that it is due to 

 toxic substances diffused from the injured cells of the exposed area. 



If this is the case why are not mitotic figures seen at the same 

 time in the exposed area? The answer to this is probably that the 

 cells are here so greatly injured that they cannot respond at once 

 to the irritation of the toxic substances, which, moreover, may at 

 first be so concentrated as to inhibit rather than stimulate the nuclei. 

 This brings up the question whether abiotic radiation is a direct 

 stimulant or depressant to mitosis. It certainly is not a direct stimu- 

 lant because, as just stated, after liminal or subliminal exposures 

 mitosis does not occur. On the other hand it probably is a depressant 

 because following intense exposures mitosis occurs in the exposed area 

 only after relatively long intervals (four to five days) and then only in 

 cells that have escaped apparent injury. This is in marked contrast 

 to the action of heat, which, as will be shown, produces abundant 

 mitosis in 48 hours and is evidently an active stimulant to cell pro- 

 liferation. 



Whether or not abiotic radiation is a direct depressant to mitosis 



