THE MICROSCOPE. 181 



New Slide for the Microscope. — For the application of 

 chemical tests to fluids under microscopical examination, the "pillar 

 slide" presents many advantages. The method usual in such cases, 

 is to place a drop of the reagent at one edge of the cover, and a bit 

 of blotting paper at the opposite edge, with or without a hair in- 

 serted between the cover and the slide to facilitate the inflow of the 

 reagent. 



If the circular pillar slide be used, then the cover must be 

 pushed so that all the space is on one side, there will thus be formed a 

 crescentic instead of an annular space. It is evident that in the 

 latter, if the space is filled with reagent it will affect the film, but 

 slowly, because evaporation takes place from the reagent itself, and 

 there is nothing to draw it between the cover and the pillar. In the 

 round pillar this is best corrected by having the diameter of the 

 cover smaller than that of the pillar, and pushing it to one side so 

 as to project a little beyond the pillar, the lunate space thus formed 

 is filled with reagent, while the rest of the edge of cover is evaporat- 

 ing and drawing upon the reagent to supply the deficiency thus 

 created, or, to hasten to the reaction, a bit of blotting paper may be 

 applied in the usual way. 



Another good way is to use a square cover, let one of the cor- 

 ners project beyond the pillar, and under this corner put the drop of 

 reagent, in this way nearly the whole of the edge of the cover will 

 be left free for evaporation, and the rapidity of the reaction will, of 

 course, be proportionately great. If desired, a different reagent 

 may be placed under each of the four projecting corners of the 

 square cover. 



The "square-pillar slide" seems, however, best adapted to this 

 class of work, with a cover the same size or smalleV than the pillar, 

 and projecting a little beyond it; the reagent will then occupy one 

 side of the square and evaporation go on from the other three sides. 

 If an oblong cover is used which projects on opposite sides of the 

 pillar, then the same or different reagents may be placed on oppo- 

 site sides of the same specimen, without danger of mixing with each 

 other. 



Talmage on Doctors. — Encourage all physicians. You thank 

 him when he brings you up out of an awful crisis of disease; but do 

 you thank him for treating the incipient stages of disease so skill- 

 fully that you do not sink as far down as an awful crisis ? There is 



