The Microscope. 215 



surface tinged by the former. If a section of stem be stained 

 throughout by a solution of eosin (2 grains to the ounce), and 

 be then placed, after washing in strong alcohol, in a^ grain so- 

 lution of Nicholson's blue made neutral, the blue will, in a short 

 time, entirely drive out the red ; but by carefully watching the 

 process, it will be seen that the different tissues will change 

 colour at different times, softer cells giving up their red and tak- 

 ing in the blue more quickly than the harder ; so that, by stop- 

 ping at the right point (which must be determined by taking 

 out a section and dipping it in alcohol, and examining it under 

 the microscope), the two kinds of cells are beautifully differen- 

 tiated by their coloring. The best effects are usually produced 

 by carmine and indigo-carmine, logwood and picro-carmine, car- 

 mine or logwood and aniline blue or green. 



To Clean Glass Slides and Covers. — First wash well in a 

 solution of soda or potash ; if this does not suffice, use the fol- 

 lowing : — Bichromate of potash, 2 ounces ; sulphuric acid, 3 

 fluid ounces; water, 25 ounces; and afterwards thoroughly rinse 

 in warm and cold water. 



Potato. — From the large amount of water which it contains 

 thin sections cannot be cut from the potato in its natural state. 

 It must, therefore, be partially desiccated, either by immersion 

 in methylated spirit for a few days, or by exposure to the air. 

 Sections may be readily obtained by imbedding and cutting in 

 paraffin. Such sections, mounted in balsam, are very beautiful, 

 the starch being seen in situ, whilst if polarized light be em- 

 ployed, each granule gives its characteristic black cross. 



Kush is to be prepared and cut as orange peel. Transverse 

 sections of this plant furnish slides of exquisite beauty. 



Vegetable Ivory, after prolonged soaking in cold water, 

 may readily be cut in the microtome. The sections should be 

 mounted unstained in balsam, and though not usually regarded 

 as polariscopic objects, nevertheless, when examined with the 

 selenite, yield very fine colors. 



