060 VERHOEFF AND BELL. 



3 minutes. After l^ hours: Exposed right eye 6 minutes; left eye, 

 3 minutes. Marked reaction with haze of cornea and loss of epithe- 

 lium in each eye. Microscopic examination: (5 days after first expo- 

 sures) : Cornea of each eye shows marked abiotic changes with loss 

 of epithelium and endothelium. Lens epithelium shows abiotic 

 changes in both eyes, but more marked in left eye. 



Histological Technique. 



Fixation: In a few of the earlier experiments the eyes were fixed 

 in a warm saturated mercuric chloride solution as recommended by 

 Birch-Hirschfeld. This was not found, however, superior to Zenker's 

 fluid for demonstrating the structure of the ganglion cells, particularly 

 the Nissl bodies, and Zenker's fluid at room temperature was there- 

 fore used for fixation in all except one of the experiments relating to 

 the retina. Before opening the eye it was usually placed in the 

 fixing fluid for about ten minutes. This pre^'ented the cornea from 

 losing its shape and the sclera and retina from becoming distorted 

 as happened when the eye was immediately opened. The eye was then 

 incised all around at the ora serrata, the vitreous body gently lifted 

 out, the lens removed and the two portions replaced in the Zenker's 

 fluid for four to six hours. Longer fixation gives less brilliant results. 

 After fixation the tissues were washed in running water twenty-four 

 hours. 



Embedding: Celloidin embedding was employed in all except one 

 experiment in order to avoid the shrinkage that results from the 

 paraffine process. 



Cornea and Iris: Meridional sections 8 to 10 /x in thickness were 

 always made, passing through the middle of the most affected part 

 of the cornea and the centre of the pupil. Tangential sections of the 

 cornea 6 to 8 yu in thickness were also frequently made. The sections 

 were stained in alum hematoxylin followed by .2% solution of water 

 soluble eosin in 80% alcohol. 



Lens Capsule: The most satisfactory method of demonstrating 

 changes in the capsular epithelium is by means of flat preparations. 

 This method was used by Hess ^^^ and later by Martin,^^^ but Birch- 

 Hirschfeld ^^ speaks of using flat sections. The method as we have 

 carried it out is as follows : The eye is opened as already described, by 

 an incision passing just behind the ciliary body all arountl. The 

 zonule is then cut all around by means of scissors, care being taken 



