Making Sections 



147 



Fig. 111. Mounting the wax block on the block holder. 



speedily as possible to avoid softening the wax in which the object is em- 

 bedded. The metal tool should be heated to a relatively high temperature 

 and applied by just touching it lightly. If the block is very long, it is also 

 desirable to build up small buttresses of wax against each side, being 

 careful not to bring these buttresses so far up the block that they reach 

 the tip of the object to be cut. The metal should now be put aside and 

 allowed to reach room temperature. Many people at this point throw the 

 block and holder into a finger bowl of water, which is all right provided 

 the water is at room temperature. However, there is no more fruitful 

 source of trouble in cutting sections than to have the knife, the block, and 

 the microtome at different temperature s. It is much better to mount the 

 blocks the day before they are to be cut and to leave them on the bench 

 to await treatment. Then final inspection is made of the block to make 

 certain that the upper and lower surfaces of the block are flat, smooth, 

 and parallel. Many people do not make the final cuts on these surfaces 

 until after the block has been mounted in the block holder. The block 

 and the block holder, after insertion in the jaws of the microtome, are 

 seen in Fig. 112. It will be noticed that set screws on the apparatus permit 

 universal motion to be imparted to the block, so that it can be orientated 

 correctly in relation to the knife. It is easy to discover whether or not the 

 edges are parallel by lower ing the block until it does not quite touch the 

 edge of the knife, adjusting it until the lower edge is parallel, lowering 

 the block again, and then comparing the relation o f the upper edge with 

 t he edge of the razor. 



Cutting Paraffin Ribbons. The first step in cutting sections on this type 

 of microtome is to make sure that every one of the set screws seen in 



