VS SUMMARY OF CURRENT RESEARCHES RELATING TO 



[B. Technique. 

 (3) Cutting', including- Embedding and Microtomes. 



Modification of Hand Microtome. — T. H. Goodspeed {Botanical 

 Gazette, 1918, 66, No. (5, 534-6, 5 figs.). Figs. 1-5 represent a simple 

 modification of the familiar hand microtome, and the author has found 

 it to be a decided improvement over the original instrument from which 

 it was derived. In the ordinary type, when cutting sections of woody 

 stems or more delicate material held in pith, it is always difficult to be 

 certain of obtaining the necessary pressure for holding the material at 

 the proper point. The steel rod which moves in or out upon the 

 turning of the single pressure screw will usually hold the material firmly 

 at its lower end, but not so firmly at its upper end, with the result that 

 the material has a tendency to wobble when the knife begins to cut the 

 section. On the other hand, when this difficulty does not arise it is 

 often almost impossible to screw up the material for the next section 

 because of the pressure of the material against the walls of the tube or 

 well. 



To obviate these rather commonly encountered difficulties in the 

 ordinary type of hand microtome the modification of it shown in the 

 figures has been devised. Figs. 4 and 5 give two views of an inner 

 " material holder." It consists of two pieces of curved steel which are 

 long enough to reach to the bottom of the tube or well (just below cc in 

 fig. 2). This inner material holder is provided with a spreading spring 

 at ed which surrounds a small steel bar cc. Each curved piece of steel 

 has a hole at aa (fig. 4) through which project the ends of the two 

 pressure screws hh (fig. 2). The manipalation of the apparatus is as 

 follows where, for example, cross-sections of a woody stem are to be 

 cut. The pressure screws hh are turned out lantil their ends at aa are 

 pulled out of the holes in the material holder. The microtome is 

 inverted and the material holder falls out. The stem or a portion of it 

 is placed between the leaves of the material holder and properly oriented, 

 and if necessary a rubber band is bound around the material holder 

 just above aa. The material holder, containing the stem, is now pushed 

 down into the well or tube of the microtome and oriented so that the 

 holes are opposite the ends aa of the turned-back pressure screws. These 

 screws are turned in, their ends pass into the holes in the material holder, 

 and pressure is finally exerted on both sides. As the pressure becomes 

 greater, the spring at dc prevents the upper ends of the material holder 

 from spreading, and ensures maximum pressure against the material at 

 these upper ends. Finally, the stem is held firmly in the centre of the 

 tube or well of the microtome between the leaves of the material holder. 

 The pressure screws are free to move up or down in their openings 

 because no appreciable pressure is exerted upon the walls of the tube 

 or well. 



In a similar manner material held in pith is very conveniently 

 arranged in this apparatus. The possibility of arranging and orienting 

 such material held in pith in the material holder outside the microtome 



