596 KARL T. WAUGH 



that the exact orientation of the eye, dorsal- ventral and anterior- 

 posterior, should be known and preserved as the paraffin hardened. 



In those eyes to be used for the study of the retina it was found 

 necessary to remove the lens because, being made harder by the 

 alcohol than the rest of the eye, the knife in striking it would have 

 a tendency to tear the more delicate retina. The lenses were 

 removed best after the eye was in the hard paraffin. A knife was 

 passed through the block just cutting off the cornea, the lens 

 was then easily picked out with a needle and the whole block 

 was reimbedded. In other eyes the lenses were removed while 

 still in xylol. 



The paraffin blocks were next cut by the microtome into sections 

 ten micra in thickness. These were taken in serial order and 

 mounted by the water method upon slides smeared with albumen. 

 The slides were warmed, washed in xylol and plunged into abso- 

 lute alcohol, after which they were run through alcohols of decreas- 

 ing strength in order to use an aqueous stain. They were then 

 stained in Delafield's hematoxylin for three hours, washed in 

 water, then counterstained over night in orange-G solution. After 

 having been removed from the last solution they were run up 

 through the alcohols again, immersed in xylol and finally mounted 

 in Canada balsam. 



Results: A diligent study w r as made of each series to learn 

 the nature of the retinal elements. There was no evidence of cones 

 to be found, either in those sections which had been cut from the 

 dorsal side downwards, exhibiting horizontal sections of the retina 

 at the middle of the eye, or in the first sections of the eye. where 

 the elements would appear in cross section (fig. 10). 



Xo cones were visible among the retinal elements in any sec- 

 tion of the eye. There were among the rods certain larger appear- 

 ances which were at first thought to be cones, but it was found 

 that these were caused by the overlapping of some of the rods or 

 by their separation from one another by an interval a little greater 

 than usual. They were not cones, as they did not take any stain 

 and in some cases they tapered away at both ends. 



Some of the eyes were cut beginning with the fundus outwards. 

 In the first few sections of the series cut in this way, where one 



