710 VERHOEFF AND BELL. 



lens system and crown glass screen (295 (x/jl) already described, the lim- 

 inal exposure was between 15 and 30 seconds, the former figure giving 

 no traces and the latter slightly more than a liminal exposure. In all 

 exposures over half a minute there was immediate heat erythema 

 and a subsequent development after a period of latency of a few 

 hours. There was a distinct but slight feeling of heat during the 

 exposure and a rather rapid extension of the erythema somewhat 

 beyond the limits of the 5 mm. stop which limited the area exposed. 

 In cases of severe exposure to the sun we are inclined to think that 

 this primary erythema due purely to the effects of heat is of consider- 

 able importance in the total results experienced. We found, as did 

 Dr. deLaroquette, that vaseline acted as a fairly complete preventive 

 as regards both primary and secondary erythema, particularly the 

 latter, while glycerine gave a slight protective action in our results, 

 more than would seem to be warranted in view merely of its trans- 

 parency to abiotic rays. From these observations and from the 

 clinical facts, often showing erythema greatly disproportionate to 

 the intensity of abiotic radiation likely to be present, it seems prob- 

 able that ordinary sunburn is due to a mixture of thermic and abiotic 

 effects of which the former are often the more prominent, although 

 they generally cannot readily be separated from the secondary abio- 

 tic effects, the development of which they tend to mask. 



Erythropsia. 



So-called erythropsia is the name of a phenomenon rather than of 

 a pathological condition. The clinical records are numerous but 

 vague. They all indicate a condition, generally very temporary, 

 in which the patient finds a more or less ruddy tinge in everything 

 seen. There is nothing definite in the tint of the coloration or the 

 period through which it is observable. It apparently runs from vari- 

 ous shades of orange and rose to a fairly full red. The most definite 

 description given of the apparent color, which evidently pertains to a 

 rather extreme incidence, is given by Fuchs ^^®, who compares it to a 

 strong fuchsin solution with a trace of eosin solution. A cursory ^-iew 

 of the clinical records indicates that the cases cited fall into three 

 general divisions. First, cases associated with neurosis such as those 

 gi\'en by Charcot and others (cited by Wyeller^^^). These clearly 

 cannot be associated with any pathological condition of the visual 



