ANOPTRAL MICROSCOPE 



1952, partly because the available phase- 

 contrast microscopes had not been developed 

 further. The halo effect in them, mentioned 

 above, continued to prove disturbing, and 

 often led to false interpretations. 



When attempts were being made to im- 

 prove this second method it became clear 

 that increasing the light absorption of the 

 soot ring to over 90 per cent gave a particu- 

 larly well contrasted image with a golden- 

 brown background against which the details 

 of the object usualh^ appeared bright (be- 

 cause of their higher optical density), but 

 were surrounded by narrow, darker zones. 

 The image was, so to speak, the reverse of 

 an ordinary phase-contrast image, with dark 

 borders instead of the bright haloes. The 

 golden-brown tint of the image was a happy 

 chance, for it is agreeable and restful to the 

 eye — a fact long known in art photography. 

 The question is now: Are the dark shaded 

 zones of the picture less disturbing than the 

 bright haloes of ordinary phase-contrast 

 microscopy? 



The answer is a definite affirmative. We 

 recognize the shape of most objects better if 



we see them lighted as they usually appear 

 in our everyday surroundings. The objects 

 are not as a rule presented in transmitted 

 light, or as silhouettes, but appear in our 

 visual field illuminated mostly from above, 

 from the side, or from several directions at 

 the same time. The diffuse light from the sky 

 is probably the most original and natural 

 form for the human eye. If we look at a 

 stone on sandy ground under this mode of 

 illumination we can see a lightly shaded zone 

 around it. If we saw the same thing as a 

 negative, in which the half-shadow borders 

 were replaced by haloes, it would be difficult 

 to apprehend the shape of the object. 



The normal image of the stone on the 

 sandy ground bears the same relation to the 

 negative as the microscopic image produced 

 by the author's second method has to the 

 image obtained by '^positive" phase-con- 

 trast. The disturbing haloes — simulating 

 phosphorescent edges — of the latter, are con- 

 verted into a virtue by their reversal, since 

 this half -shadow bordering assists the apper- 

 ceptive faculty and produces an almost plastic 

 effect. (Fig. 3). 



/ 



^^*. 



svib^_ .'»: 



Fig. 3. Parts of two (2) epithelial cells from the oral mucosa seen by ordinary piiase contrast (a) and 

 by the anoptral method (b). From the latter we obtain an illusion of third dimension (depth) which is 

 due to the shadow-effects around the cell borders. Reichert achromats lOOX. Magnification 1350X . 



479 



