10 HOW TO USE THE MICROSCOPE 



are not always of best quality, and for dissecting 

 purposes a good straight and true pair costs 

 Is. 6d. A curved pair wiU also be very useful — cost, 

 about 2s. 6d. The needles, mounted in plain cedar 

 handles, are only 2d. each. A curved pair of scissors 

 can be added to the stock of tools when needed ; they 

 cost at least 3s. 6d. These tools should be kept 

 thoroughly clean and free from rust ; the knife or 

 scalpel will require sharpening to a smooth, keen 

 edge on a hone from time to time. Good clean 

 work cannot be done with dull or dirty tools. 



The needles required are easily prepared at home. 

 All that needs to be done is to fix needles of different 

 sizes in wooden handles. The hafts of worn-out 

 camel-hair brushes serve weU. They should be 

 boimd at the end in which the needles are to be 

 inserted with strong waxed thread. The eyes of 

 the needles must be broken off, and after a small 

 bore has been made with a needle-point in the 

 wooden hafts each needle can be forced into a secure 

 position by means of a pair of small phers. 



In order to deal with some parts of an object, 

 curved or bent needles may be necessary. The 

 desired curvature is easily effected by heating the 

 needle in the flame of a spirit lamp, and bending it 

 while red-hot. The heat, of course, takes the hard- 

 ness out of the steel, but this is quickly renewed by 

 raising it once more to a red heat, and plunging it 

 quickly into water. In the absence of a spirit lamp, 

 the needles may be heated in a candle or gas flame, 

 but such flames blacken them with soot, which will 

 have to be carefully wiped off. 



The student will also find use for a few camel- 



