226 



MICROSCOPICAL RESEARCH IN THE 



a mixture of hard and soft paraffine,* heated to about 50° C. 

 After remaining for half an hour or less in the harder paraffine, 

 kept at a steady temperature, they are ready for imbedding. For 

 this purpose a small paper box may be used ; or, much better, a 

 box made of two pieces of type-metal, as used in Professor 

 Leuckart's laboratory. As will be seen 

 from the accompanying diagram, each 

 piece of metal has the form of a carpenter's 

 square, with the end of the shorter arm 

 triangularly enlarged outward. A conve- 

 nient size will be found in pieces measuring 

 7 (long arm) by 3^^ (short arm), and 7™"^ 

 high. With such pieces a box may be 

 constructed at any moment by simply 

 placing them together on a round plate of 

 glass, which has previously been wet with 

 glycerine and gently warmed. The area 

 of the box will evidently vary according 

 to the position given to the pieces, but the 

 height can be varied only by using different 

 sets of pieces. In such a box the paraffine 

 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. 



It is well to imbed in a thin layer of paraffine, so that the 

 object, after cooling, may be cut out in small cubical blocks, which 

 may be easily fixed, for cutting, to a larger block of hard paraffine. 



V. — Cutting. 



Objects are cut dry with a microtome,''' and the rolling of the 



sections may be prevented by holding a thin narrow spatula over 



the edge of the knife while cutting. The spatula may be made of 



brass, or paper fastened to a flattened needle. The spatula should 



* The ratio of combination must be determined by experiment, since it will 

 depend on the quality of the paraffine and the temperature. Two parts of hard to 

 one of soft, work very well for the winter temperature of Naples. 



t An improved form of Thomas' microtome is made by Rudolph Yung, Heidel- 

 berg, Hauptstrasse 15. The carrier is moved by a micrometer screw, and the 

 holder can be adjusted in any desired position. 



