120 THE MICROSCOPIST. 



As most dissections are made under water, convenient troughs 

 are necessary. They may be from two inches to a foot long 

 and of a proportionate breadth and depth. Earthenware, or 

 glass, is the best material. One may be prepared with a flat 

 piece of cork cemented to the bottom, inside, by marine glue. 



Loaded corks are flat pieces of cork with sheet lead cemented 

 to their under surface with Burgundy pitch, so that they may 

 readily sink in the water. To these corks the subject to be 

 dissected is fastened with pins. 



For vermiform animals, long, narrow, semicylindrical plates 

 are best ; to the convex surface of which they may be fastened, 

 with the legs (if any, as in Myriopoda) hanging along the sides. 



Rests are inclined planes of wood ; one on each side of the 

 trough holding the specimen. If the Dissecting Microscope, 

 represented by Fig. 5, is used, neither rests nor troughs will 

 be required, other than are furnished with the instrument ; 

 unless it be troughs for specimens not immediately under exa- 

 inination. 



In addition to these instruments, a small syringe, camel's- 

 hair pencil brushes, &c. &c., will be found useful. 



For some objects, which are with difficulty kept in place for 

 dissection, a little plaster may be mixed to the consistence of 

 thin cream, and by means of a brush may be coated over those 

 parts which are desirable to be fixed; then, by placing it in a 

 small box or other suitable mould, the plaster may be poured 

 round it, and allowed to harden. In this case a loaded cork 

 is unnecessary, the weight of the plaster being generally suf- 

 ficient. The plaster may be colored with ink, &c., if its white- 

 ness is fatiguing to the eye. 



Before dissection, a good light should be thrown upon the 

 object by means of the condensing lens (Fig. 15). 



A dissecting microscope is also generally necessary. This 

 may be one specially designed for the purpose, as Fig. 5; or the 



