78 



CHAPTJiR, Vil. 



G-iESBEECHT now makey trays of photographic fihns, which 

 being transparent facilitate orientation under the dissecting 

 microscope. 



To make paper thimbles, take a good cork, twist a strip of 

 paper several times round it so as to make a projecting 

 collar, and stick a pin through the bottom of the paper into 

 the cork. For work with fluid masses, such as oelloidin, 

 the cork may be loaded at the bottom by means of a nail 

 or piece of lead, to prevent it fro.n floating when the whole 

 is thrown into spirit or other liqaor for hardening (Fig. 2). 

 Leuckhaet's Imbedding Boxes are made of two pieces of 

 type-metal (Fig. 3). Bach of these 

 pieces has the form of a carpenter's 

 " square " with the end of the shorter 

 arm triangularly enlarged outwards. 

 The box is constructed by placing the 

 two pieces together on a plate of glass 

 which has been wetted with glycerine 

 and gently warmed. The area of the 

 box will vary according to the 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 one centi- 

 metre in height, and one of two centi- 

 metres, each being eight centimetres 

 in length, and three 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. Zuol. Stat. Necipel, 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 



Fig. 3. 



