EFFECTS OF RADIANT ENERGY ON THE EYE. G91 



These observations are in accord with those of Bach made twenty 

 years ago. Investigating the possible effect of fatigue upon the 

 ganghon cells of the retina, Bach ^^ made a careful comparison of 

 retinae of rabbits exposed and unexposed to light. In some cases 

 eyes were exposed to a Welsbach light for 20 hours. Alcohol or 

 sublimate fixation was used and the sections stained by the original 

 Nissl method or in thionin. Contrary to the previous observation 

 of Mann^^^ and the later observations of Birch-Hirschfeld,^^ he was 

 unable to find that the ganglion cells of the exposed eye differed in 

 any way from those of the unexposed. He says: "Ich geh zu, dass 

 ich langere zeit im Zweifel war und bald diese bald jene Veranderimgen 

 gefunden zu haben glaubte, jedoch alles anscheinend Gefundene liess 

 mich die controle wieder als Irrthum erkennen. Es ist eben zu 

 bedenken, dass trotz gleicher Schnittdicke, trotz des genau gleichen 

 Verfahrens beim Farben etc. immerhim sich tinctorielle Unterschiede 



ergeben konnen Ich muss bemerken, dass auch in normalen 



Netzhauten an den Ganglienzellen sich Unterschiede besonders hin- 

 sichtlich der Menge vmd Anordnung, der Form der farbaren Plasma- 

 schollen ergeben, das auch normalen Weise Vacuolen in dem Zellleib 

 gefunden werden, das die Kerne sich verschieden verhalten konnen — 

 kurz ich konnte an den beleuchteten Netzhauten Nichts warhnehmen 

 oder vermissen was ich nicht an normalen, an verdunkelten Netz- 

 hauten auch wahrgenommen oder vermisst hatte." 



Birch-Hirschfeld ^^ states that also by means of the vital methylene 

 blue staining method he found chromatolysis, vacuolization, and other 

 changes in the retinal ganglion cells of eyes that had been exposed 

 to ultra violet light, and that such changes were absent in normal eyes. 

 I find, however, by this method in the normal rabbit's retina, appear- 

 ances that correspond exactly to those described and depicted hy 

 Birch-Hirschfeld, including particularly the "vacuoles" in the gan- 

 glion cells which are abundantly present. The "vacuoles" at first 

 glance appear to be really such, but a careful study of them strongly- 

 suggests that they are here due to the cell reticulum staining more 

 promptly and deeply than the cytoplasm proper, and thus producing 

 an appearance of rounded spaces. I have also examined the retina by 

 the vital methylene blue method 48 hours after the exposure of one 

 hour to the magnetite arc and lens system (Exp. 78). The results 

 obtained were identical with those obtained in the case of an un- 

 exposed normal retina. 



In addition to the experimental investigation just discussed, Birch- 

 Hirschfeld^^ has reported clinical observations in five cases of pho- 



