74 



IMBEDDING METHODS. 



FIG. 3. 



position given to the pieces, but the height can be varied only by 



using different sets of pieces. Two sets will be sufficient for most 

 work, one set of 1 centimetre in height, and 

 one of 2 centimetres, each being 8 centi- 

 metres in length, and 3 in breadth. To make 

 the box paraffin-tight, so that it will hold the 

 melted paraffin long enough in the liquid 

 state to permit of the objects being carefully 

 orientated in it, MAYER (Mitth. Zool. Stat. 

 Neapel, iv, 1883, p. 429) first smears the glass 

 plate with glycerine, then arranges the metal 

 " squares," and then fills the box with col- 

 lodion, which is poured out again immedi- 

 ately. As the ether evaporates, a thin layer 

 of collodion remains behind, which suffices 

 to keep the paraffin from running out. Even 

 without the collodion, the mere cooling of 

 the paraffin by the metal will generally 



suffice to keep it in long enough for orientation, if it is not in a 



superheated state when it is poured in. 



In such a collodionised box the paraffin may be kept in a liquid 



state by warming now and then over a spirit lamp, and small objects 



be placed in any desired position under the microscope (Journ. Roy. 



Mic. Soc. [N.S.], ii, p. 880). 



A lighter form of " squares," made of brass, and devised by 



ANDRES, GIESBRECHT, and MAYER, is described loc. cit. (See Journ. 



Roy. Mic. Soc., 1883, p. 913.) A more complicated sort is described 



by WILSON in Zeit. wiss. Mik., xxvii, 1910, p. 228, for use with 



imbedded threads to serve as orientation guides. See " Orientation." 

 FRANKL (Zeit. wiss. Mik., xiii, 1897, p. 438) builds up boxes with 



rectangular blocks of glass, which may be found convenient, but are 



more expensive than the metal squares. 



SELENKA has described and figured another sort of apparatus having 

 the same object. It consists of a glass tube, through which a stream 

 of warm water may be passed and changed for cold as desired, the 

 object being placed in a depression in the middle of the tube (see Zool. 

 Anz., 1885, p. 419). A simple modification of this apparatus, which 

 any one may make for himself, is described by ANDREWS in Amer. 

 Natural., 1887, p. 101 ; and a more complicated imbedding and orienting 

 box, seldom necessary, is described by JORDAN in Zeit. wiss. Mik., xvi, 

 1899, p. 32. 



To imbed in a watch-glass, the object, previously saturated with 

 paraffin, is put into a (preferably very concave) watch-glass con- 



