i HINTS ON DISSECTION 13 



(which is simply to keep the cork-board from floating in water) down- 

 wards. Or, place a few strips of sheet lead in the bottom of the 

 dish, and then pour in 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 1 8 inches x n inches and f-inch thick, and nail round its edge 

 a strip of wood about | 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 \ -inch brass- 

 tubing, about 6 inches long, into a heavy block of wood, about 3 inches 

 in diameter, and coiling round it, in a close spiral, one end of a piece of 

 thick wire, which can be raised and lowered on the tube. Leave 6 or 7 

 inches of the wire standing out at right angles, and bend the free end 

 into a loop to carry the lens. 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 or 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, 1 which can be diluted as it is wanted. For preserving 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 5 per cent., 

 according to circumstances should be used, or methylated spirit. If 

 formaline is not available, use strong methylated spirit (i.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 of chloroform. 



1 A 40 per cent, solution of the gasforwtc aldehyde. 



