76 



IMBEDDING 



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be sufficient for most work, one set of 1 cm. in height, and one of 

 2 cm., each being 8 cm. in length, and 3 in breadth. To make the 

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

 enough m the liquid state to permit of the objects being carefully 

 orientated in it, Mayer {Mitih. Zool Stat. Neapel, iv, 1883, p. 429) 

 first smears the glass plate with glycerin, then arranges the metal 

 squares," and then fills the box with collodion, which is poured 

 out again immediately. 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 {J own. 

 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. Sac, 1883, p. 913.) A 

 more complicated sort is described by 

 Wilson in Zeit. zviss. Mik., xxvii, 1910, 

 p. 228, for use with imbedded threads to serve as orientation 

 guides. See " Orientation." 



Frankl {Zeit. zviss. 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. 



Selknka 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 depHlssion 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 (previously rubbed around with 

 glycerin), the object, saturated with paraffin, is put into a 

 (preferably very concave) watch-glass containing molten paraffin. 

 After this has been solidified by cooling (see next chapter), a 

 block containing the object is cut out of it, and mounted on the 

 object-holder of the microtome (this is, of course, applicable to 

 other masses, such as celloidin). 



Fig. 3. 



