SPECIMENS IN A MOIST STATE. 



803 



Fig. 963. 



Dissolve and filter the solution. Alcohol is often used, but it usually 

 makes all colours alike brown. It is useful for delicate specimens 

 which are required for dissection. Pyroligneous acetic acid diluted 

 with from 3 to 5 parts of water is also very generally employed. 

 Specimens, however, in the acid are apt to become pulpy and brittle 

 after a few years, so as not to admit of being handled ; most colours 

 are altered by it. Before being put in jars, fresh specimens should 

 be kept for a month or more in the solution, so 

 as to allow any colouring matter and other impuri- 

 ties to be separated, otherwise the preparation will 

 become obscure, and require to be re-adjusted. The 

 mouth of the glass jars may be conveniently covered 

 with India rubber, or, in the case of glasses of small 

 diameter, with a watch glass secured by sealing wax, 

 or by circular glass covers cemented by a lute com- 

 posed of resin 1 part, wax 2 parts, and vermilion 1 

 part. The glass cover on the top of the jar may be 

 either luted or held in its place by a metallic ring 

 (fig. 963 a), which is fitted carefully to it, and 

 covers a portion of the glass lid. Two grooves may 

 be made on the inner side of the rim at the top of 

 the jar for holding a piece of whalebone, to which 

 the specimen may be attached by means of a thread, as seen in the 

 figufe. In the case of dry preparations, the metallic ring answers 

 well. 



It is difficult to keep the solution of salt in the preparation jar. Sir 

 Robert Ohristison says : — " The most efiectual method, when the mouth 

 of the jar does not exceed 2 or 2J inches in diameter, is to have a 

 space half-an-inch or more at the top of the fluid, to clean and dry 

 the top of the jar thoroughly, to drop melted sealing-wax on the upper 

 surface of the top, so as to form a uniform ring over it, to place over 

 the mouth a watch-glass of such size as to cover the whole lip, and 

 even to overhang it a little, to press this gently down with one finger, 

 and to fuse the wax between the top of the jar and the watch-glass, 

 by moving a large spirit flame around the edge." Where the mouth 

 of the jar is large, then a round flat piece of glass may be used, or 

 sheet caoutchouc. The latter, after being gently heated, is stretched 

 moderately, not strongly, by one, or still better, by two persons, while 

 a third secures round the neck two or three folds of stout twine as a 

 temporary ligature. A stout thin cord is then drawn steadily and 

 tightly round three or four times above the former, taking care that 

 the caoutchouc is not cut, and that the turns of the twine lie regularly 

 above each other j and finally, that a secure knot is made. 



Fig. 963. Jar for holding wet or dry preparations, the glass cover at the top being held 

 in its place by a metallic ring. 



