506 BIOLOGICAL EFFECTS OF RADIATION 



with final healing (9 months). After a single irradiation of 250 per cent 

 of a human erythema dose a 9 months' observation shows the corneal 

 epithelium disturbed in regularity and order of the cells and their staining 

 power in the different layers. There is a degeneration of the corneal 

 cells and a beginning degeneration of the inner horny layer and the 

 normal content of the outer layer is diminished. The retina plainly 

 shows (from a single dose) ganglion-cell changes due to definite irradiation 

 damage. 



Cremer (54) describes a cataract with acute inflammation of the 

 cornea in a child as a result of irradiation, following a dosage which did 

 produce similar damage to an animal. In the rabbit, cataract is always 

 caused by an epilation dose, but this does not occur with such constancy 

 in man. The lens changes do not appear until a dosage up to 1340 r, 

 or 270 per cent of human skin dose is applied (302). If the maximum 

 safe dose for the lens of the rabbit is taken as 100 per cent (or 180 per cent 

 human erythema dose), for the cornea and conjunctiva it is 200 per cent, 

 for retina and ganglion cells 100 per cent, for the conjunctiva 200 per cent. 

 The lens is more sensitive to permanent damage than the hair papillae 

 of the lid (168, 301, 302). The dosage necessary to produce chronic 

 damage is not so great as that producing acute damage, provided that 

 sufficient length of time is allowed to pass for the chronic changes to 

 occur (301, 302). 



Desjardins (72) has very carefully reviewed the experimental work 

 done on the eye. He points out that the conjunctiva and the eyelids 

 have about the same sensitivity as the skin and the resultant changes, 

 while they are perhaps slightly more severe, pass through the same cycle 

 of latent period, injection of vessel, loss of hair, inflammation, and ulcera- 

 tion. The cornea, iris, ciliary bodies, and retina are increasingly more 

 resistant in the order named. Changes may occur in the capillaries in 

 any portion of the eye. These are identical with changes described for 

 the capillaries elsewhere {i.e., the skin). 



The painful conjunctivitis and photophobia following exposure of 

 the human eye to ultra-violet radiation are well known. Verhoeff and 

 Bell (361) have done the best work on the effects of ultra-violet radiation 

 on the eye, showing that in rabbits destructive changes can be brought 

 about in the retina, as well as in the cornea and the lens. There is 

 considerable discussion about the effects of various wave-lengths and 

 whether or not the effects are primarily due to ultra-violet or infra-red 

 after absorption (156, 191, 218). 



EAR 



Desjardins (72) has pointed out that very little work has been done 

 on the effect of radiation upon the ear. Most of the data reported 

 concerned cases in which abnormal conditions, either surgical laceration 



