1899] MICROSCOPICAL JOURNAL. 285 



tation being practiced with each step. Care must be 

 taken not to use too small a quantity of alcohol or the 

 cells will not be well dehydrated. 



Clear in carbol-xylol (carbolic acid one part,xylol three 

 parts), allow the blood to settle in a large test tube or 

 conical glass, draw off as much of the fluid as possible 

 with a bulb pippete and add thin xylol balsam. 



Keep in a well stoppered bottle and when wanted for 

 use shake until the blood is thoroughly mixed with the 

 balsam, with a small glass rod transfer a drop to a clean 

 slide and superimpose a cover-glass. A neat and per- 

 manent preparation is the result. — A. M, 8. 



MICROSCOPICAL APPARATUS. 



The Power Limit.— S. B. Twitchell (Ohio Med. Journal, 

 January 1, 1898), discusses the resolving- power of the mi- 

 croscope. Up to the present, Nobert's twentieth band, 225,- 

 190 lines to the inch, has never been resolved, and theoret- 

 ically, with white light, only 146, 543 lines per inch can be 

 distinguished. By utilizing, however, the shorter actinic 

 rays and a photographic plate, theoretically 193,037 lines 

 per inch should be resolved, that is effects beyond the pos- 

 sibility of ocular vision. 



MICROSCOPICAL MANIPULATION. 



To Cut Cells in Glass Slips.— A hole is bored through 

 the glass very easily with a piece of copper tube running 

 in a lathe, the end of the tube resting on the glass. The 

 tube must be charged with emery powder and oil. A thin 

 cover glass is then cemented on the slip, over the hole, with 

 gold size, or ordinary gum may be used for this purpose 

 and answers very well. I often confine a live insect in this 

 way, and view it at both sides with a Lieberkuhn mirror 

 or a side reflector. In this case I pasted the cover on very 

 lightly with gum. Most insects possess a beauty when 

 viewed alive which they lose after death. 



