EFFECTS OF RADIANT ENERGY ON THE EYE. 641 



central portion of the cornea and rapidly shading off toward the 

 periphery, where, as is shown in Figure 2, the energy received per unit 

 area is greatly decreased. Thus the mere appearance of the affected 

 area shows in a qualitative way proportionality between the exposure 

 and the following lesion, a proportionality shown to be definite in the 

 experiments we have described. 



The Effects of Repeated Exposures to Abiotic Radiations. 



A natural corollary of the proposition that the pathological effects 

 of abiotic rays on the cornea are proportional to the energy is that at 

 least for brief intermissions the effects of repeated short exposures 

 are equivalent to their sum in a single long exposure. This is, of 

 course, subject to the general qualification that reparative processes 

 are steadily going on, tending rather gradually to the healing of 

 injured tissue. An ordinary case of photophthalmia completely 

 disappears in less than a week and repair is going on all through this 

 period. It is obviously possible also that apparent complete recovery 

 may still leave the tissues slightly hypersensitive to further injury. 

 We therefore set about investigating the effects of repeated exposures, 

 both liminal and subliminal, to ascertain the additive effect of short 

 exposures, the rate at which the reparative processes proceeded, the 

 completeness of their work, and the possible effects of secondary 

 reactions incidental to the main pathological effects. There was a 

 bare possibility that something akin to anaphylaxis might occur 

 owing to the development of toxins, and this phase of the matter had 

 also to be investigated. 



In the case of abiotic radiation affecting a large portion of the body 

 it seems possible that a general constitutional effect might occur owing 

 to the absorption of the toxic substances produced. Such an effect 

 is known to occur after severe burns from heat. In the case of the 

 eye, however, the amount of tissue affected is of course too slight 

 for any such effect to be expected. 



The experiments on subliminal exposures repeated at intervals of a 

 few minutes to an hour or more, here summarized, show clearly that 

 within 24 hours the energy effects are simply additive, intermissions 

 within this time evidently being too short for reparative action to 

 take place. The discovery of this fact is important since it shows that 

 with any source of abiotic rays it is the total exposure that counts, 

 and that the effect of this total exposure, if within 24 hours, can be 

 calculated from the data already given. 



