46 



MICROSCOPY OF THE LIVING EYE 



back of the cornea and still to observe it (O) both through 

 an area of corneal tissue in front whose transparency is not 

 impaired by the passage of the illuminating rays, and also 

 against an unilluminated visual background. It should be noted 

 that this diagram (Fig. 15), representing a horizontal section 

 through the illuminated eye, serves to depict either a ribbon- 



FiG. 13. — Pattern of slit-lamp and of the Cpazski binocular 

 microscope, made by Messrs. Theodore Hamblin, Ltd. 



like beam issuing from a vertical slit, or a minute round or square 

 beam, the only difference being the very practical one that the 

 slit beam, with its more or less limitless vertical range, can 

 illuminate a much greater vertical area for observation, whilst still 

 affording the required principles of restricted illumination. It 

 will also be noted (Fig. 15) that the observer has chosen his line 

 of observation, O, in a direction to avoid the dazzle along the 

 axis of specular reflection (sr) from the mirror-like epithelial 



