12 



MICROSCOPICAL DIAGNOSIS. 



notice. A nose-piece will prove one of the most useful accessories 

 that the working microscopist can possess. By the aid of this, a 

 low power can be used for finding the objects, when without delay 

 it can be examined with a higher power. 



A camera lucida or neutral tint reflector .s useful for pur- 

 poses of drawing. As seen in the figure, the image is thrown upon 

 a piece of paper where its outlines may be traced. The prism con- 

 trived by Dr. Wollaston is the one in most general use. It can be 



Fig. 4. Camera Lncida, or Neutral Tint Reflector. {Baiisch 6 Lomb. ) 



purchased for about $6.00. As a substitute for a neutral tint 

 reflector, Mr. T. B. Jennings recommends the following: A hole is 

 cut in a flat cork, of sufficient size so that the cork just slips over 

 the end of the eye-piece without its cap. A transverse slit is made 

 beneath the hole and a common cover-glass inserted, at an angle of 

 45 to the optical axis of the microscope. 



An eye-piece micrometer is a very useful accessory. Knowing 

 the value of the spaces to which it is ruled, objects can be accurately 

 and quickly measured. Of course the relative distance between the 

 rulings will depend upon the objective used, the length of the tube of 

 the microscope, and the eye-piece, By always using the draw-tube 



