THE PRESERVATION OF MARINE OBJECTS 73 



for the purpose of examining internal structure with or without the 

 aid of the microscope, and for such purposes strong spirit is one of 

 the best hardening agents that can be employed. 



Formaldehyde is another very good preservative. It is a colour- 

 less liquid, and should be considerably diluted for use, a two per cent, 

 solution being quite strong enough for all ordinary purposes. It 

 possesses some distinct advantages as compared with spirit. In 

 the first place, it does not destroy the natural colours of objects 

 to the extent that spirit does ; and, although a hardening agent as 

 well as a preservative, it does not harden soft structures by the 

 extraction of the water they contain, and therefore does not cause 

 them to become shrivelled or otherwise distorted. It will also 

 occur to the reader that, since a small bulk of formaline represents 

 a large volume of the diluted preservative, it is very conveniently 

 stored, and a very small bottle of it taken for outdoor work may, on 

 dilution with water, be made to yield all that is required for the 

 preservation of the takings of a successful day, or even of a longer 

 period. Formaldehyde is usually sold in solution of about forty per 

 cent, strength, and for the preparation of a two per cent, solution it 

 will be found convenient to provide a glass measure graduated either 

 into cubic centimetres or fluid ounces and drams. One hundred 

 volumes of the original solution contain forty of pure formaldehyde, 

 and if water be added to make this up to two thousand volumes, a 

 two per cent, solution is obtained. Thus, one hundred cubic centi- 

 metres of the original solution is sufficient to prepare two litres 

 (three and a half pints) of suitable preservative. 



A very good preservative liquid may be made by dissolving two 

 ounces of common salt, one ounce of alum, and two or three grains 

 of corrosive sublimate (a deadly poison) in one quart of water, and 

 then, after allowing all sedimentary matter to settle to the bottom, 

 decanting off the clear solution. This mixture is known as Goadby's 

 fluid, and is well adapted for the preservation of both animal and 

 vegetable structures. It does not cause any undue contraction of 

 soft tissues, and, as a rule, does not destroy the natural colours of 

 the objects kept in it. 



Glycerine is valuable as a preservative for both animal and 

 vegetable objects, and especially for the soft-bodied marine animals 

 that form such a large percentage of the fauna of our shores. It 

 maintains the tissues in a soft condition, and preserves the natural 

 tints as well as any liquid. 



An inexpensive preservative may also be made by dissolving 



