CASES. 



73 



of the case. The pin bearing the insect is passed through 

 both sheets of paper until its point penetrates the wood. 

 Thus three points of support are obtained. Other substitutes 

 for cork have been proposed, corn stalks elder pith pita, etc., 

 but their use is attended with this disadvantage, that the sap 

 which they contain produces by fermentation an acid which 

 corrodes a pin. 

 Storage cases for insects are usually made in pairs, and 



Fig. 26. 



should have the two parts fitted together by tongue and 

 groove. This will be very effectual in excluding vermin. 



A large proportion of the alcoholic specimens of any col- 

 lection will be kept in what are known as homoeopathic vials 

 and various ways for arranging and keeping these have been 

 devised. The common method is by laying them down in 

 shallow drawers, but this has the disadvantage of injuring the 

 cork by keeping it constandy soaked with alcohol. Mr. 

 Emerton has suggested a handy form which is well adapted 



