72 THE SEA SHORE 



practice, and illustrated notes prepared for the purpose we suggest 

 will undoubtedly be of great value to the student. Further, 

 though it may often be necessary to set specimens aside in a 

 preservative fluid until one has the leisure to examine their 

 structure, it should always be remembered that they never im- 

 prove by keeping, also that they are rarely in such good condition 

 for dissection after saturation with the preservative as when 

 perfectly fresh. 



One of the most convenient preservatives for general use is 

 undoubtedly methylated spirit. This is alcohol that has been 

 adulterated in order to render it undrinkable, so that it may be 

 sold free from duty for use in the various arts and manufactures 

 without any danger of its being employed for the concoction of 

 beverages. It may be used just as purchased that is, in its 

 strongest condition for many purposes, but in this state it has 

 a powerful affinity for water, and will rapidly abstract water from 

 animal and vegetable objects, causing the softer ones to become 

 hard, shrunken, and shrivelled, often to such an extent that they 

 are almost beyond recognition. 



By diluting the spirit, however, we satisfy to a great extent its 

 affinity for water, and thus prevent, or, at least, reduce the action 

 just mentioned. A mixture of equal quantities of spirit and water 

 is quite strong enough. Unfortunately the common methylated 

 spirit of the shops produces a fine white precipitate, that gives 

 the whole mass a milky appearance, when it is diluted. This is 

 due to the presence of mineral naphtha, which is added in a 

 certain fixed proportion in accordance with the Government 

 regulations. But it is possible, by special application, to obtain 

 the ' non-mineralised ' or ' ordinary ' methylated spirit of former 

 years, though not in small quantities, and this liquid dissolves in 

 water without the formation of a precipitate. It should be noted, 

 however, that the use of the spirit as a preservative is in no way 

 interfered with by the presence of the mineral naphtha, the only 

 disadvantage of this impurity lying in the fact that the milkiness 

 consequent on dilution prevents the objects in a specimen jar from 

 being observed without removal. 



We have just referred to the hardening action of strong spirit 

 as a disadvantage, and so it is when it is required to preserve soft 

 structures with as little as possible of change in general form and 

 appearance ; but there are times when it becomes necessary to 

 harden these soft structures in order that sections may be made 



