CHARACTERS OF ANIMALS. 135 



large, it is proper, before immersing them, to inject a quan- 

 tity of the spirits into their interior, to prevent incipient 

 putrefaction, and consequent discoloration of the spirits. 

 In order to suspend the specimen in the fluid, it is affixed 

 by a thread to a float of clean cork, or, which is much bet- 

 ter, of glass, and sometimes to a slip of wood fixed across, 

 In many cases, the introduction of a bubble of air into the 

 specimen itself, by means of a blowpipe, will effectually 

 secure the object in view. 



The greatest inconvenience that attends the use of ob- 

 jects preserved in alcohol, arises from the evaporation of 

 the spirits, and the risk of having the specimen destroy- 

 ed by putrefaction before the change is observed. When 

 the glass is closed by cork merely, the evaporation some- 

 times takes place very rapidly, by its capillary attraction, 

 and this effect is sometimes accelerated by a thread from 

 the object passing through the mouth of the vessel along 

 with the cork. The evaporation of the spirit may be re- 

 tarded by giving it a thin covering of fixed oil ; or, it may 

 be altogether prevented, by covering the mouth of the ves- 

 sel with two or three folds of bladder bound round the 

 edges tightly with pack-thread. If the layers of bladder 

 are well coated with mucilage of gum-arabic, glue, or the 

 white of an egg, the utmost security will be obtained. If 

 a piece of tin-foil be coated on the under side with glue, 

 and then tied closely over the mouth of the vessel, and 

 again coated with glue on the outside, and a slip of bladder 

 tied closely over it, every risk may be avoided. The sur- 

 face of the bladder may now be coated with coloured var- 

 nish, to improve the appearance of the preparation. The 

 advantage attending a covering of glue or mucilage, over 

 the common varnish frequently used, arises from their inso- 

 lubility in the alcohol. Objects preserved in alcohol may 

 be taken out for the purpose of examining their structures 

 after carefully macerating them in water. 



