I HINTS OK DISSECTION 13 



dish with the lead (which is simply to keep the cork-board from float- 

 mg in water) downwards. Or, place a few strips of sheet lead in the 

 bottom of the dish, and then pour jin some melted paraffin-wax into 

 which a little lamp-black has been stirred, so as to make a layer half an 

 inch or more in thickness. 



For larger animals than the frog, in addition to a. larger dish, a 

 dissecting board will also be required. Get a piece of soft deal or pine 

 about 18 inches x n inches and f inch thick, and nail round its edge 

 a strip of wood about j inch x \ inch, so as to form a projecting rim. 



9. A magnifying glass. Any good pocket lens or a common watch- 

 maker's glass will answer the purpose. As it is often desirable to 

 have both hands free while using the lens, a stand of some kind is 

 useful. One of the simplest is made by fixing a piece of thick flexible 

 wire, 6 or 8 inches long, into a heavy block of wood, 3 or 4 inches in 

 diameter ; the free end of the wire is bent into a loop to carry the lens, 

 which can thus, by bending the wire, be raised or lowered as required. 

 Or, get a piece of narrow clock-spring, about 13 inches long, and rivet 

 one end of it to the outside of the rim of a watchmaker's glass, and 

 the other to a small piece of zinc or brass ; on passing the spring round 

 the head, the lens is kept in place at the eye without exertion. 



10. Medium and small-sized pins. Large blanket pins are useful for 

 fixing down larger animals. 



11. A small sponge and a duster. 



12. One or more wide-mouthed bottles ox Jars, containing a. preserva- 

 tive in which to place your subjects after each day's work. The most 

 convenient preservative for the purpose in most cases is the fluid sold as 



formaline,^ which can be diluted with water as it is wanted. For pre- 

 serving your dissections from day to day, a I per cent, solution of 

 formaline is strong enough in many cases — i.e., I cubic centimetre of 

 formaline to 99 c.c. of water, or three-quarters of a dram of formaline to 

 half a pint of water. For permanent preservation, a stronger solution 

 — 2 to 4 per cent., according to circumstances — should be used, or 

 methylated spirit. If formaline is not available, use strong methylated 

 spirit {/.e., about 90 per cent.) diluted _with one-third of its bulk of 

 water. 



13. A plentiful supply of clean water. 



14. An ounce or two oi chloroform. 



^ A 40 per cent, solution of the gm formic aldehyde. 



