On the Formation of Multiple Images in the Normal Eye. 245 



If the distance between the eye and the incandescent filament is 

 made much more than 8 feet, or if a lens of shorter focus is employed, 

 the multiple images become blurred and indistinct ; at a distance of 

 20 feet with a lens of 3 inches (7'6 cm.) focal length, the separate 

 images appeared to have coalesced, but the band of light was crossed by 

 a very large number of hazy dark lines at right angles to its length 

 and at fairly equal distances apart. 



Thinking that the original images had been resolved into still simpler 

 elements, I endeavoured to ascertain how many elements were de- 

 veloped from each image. Fixing my attention upon a conspicuous 

 image near the end of the row, I moved a convex lens slowly forwards 

 in front of the slit, and carefully watched the changes which occurred. 

 It was found very difficult to follow them satisfactorily, but the con- 

 clusion arrived at was that the space corresponding to a single image 

 was ultimately crossed by from fifteen to twenty dark lines ; hence, 

 assuming twenty-five images, the total number of elements would be 

 four or five hundred. 



Taking the diameter of the pupil when feebly illuminated to be 

 J inch, these latter observations seem to indicate some fairly regular 

 anatomical structure in or near the crystalline lens, and composed of 

 cells measuring about -^-^ inch (O'Ol mm.) in length or breadth. It 

 has been suggested to me that the cause may be found ia the endo- 

 thelium on the anterior surface of the lens, the cells of which are 

 polyhedral and flattened, and about 0'02 mm. in diameter. Their 

 dimensions appear to be too large, but perhaps the agreement is as 

 close as could be expected. 



I do not know of any structure sufficiently coarse-grained to account 

 for the images of which twenty-five or thereabouts occur in a row. 

 The mesh of a network which would explain these should be about 

 T |- inch (0-2 mm.) in length, and nothing of the kind is, I believe, to 

 be found in the eye. Probably, however, the effect is a composite, or 

 rather a differential one, like that of the two pieces of gauze used in 

 photographing the lamp. If light passed through two or more super- 

 posed nets having fine meshes, dark bands would generally be produced, . 

 which would take the form of a network of a coarser mesh than those 

 of the nets themselves possibly much coarser, as would be the case if 

 the two nets were nearly alike in structure. 



The seven or eight images referred to in the description of the first 

 observation are, as before mentioned, undoubtedly due to the sections 

 or sutures of the lens. 



