Chapter IV: Simple Section Methods 



35 



of paraffin. As the paraffin melts transfer drops of it to the edge of the 

 tissue, which has been previously placed on the cork. The paraffin-<x)ols 

 and holds the tissue fast. 



Another and better method of handling a small object is to imbed it 

 in a piece of hardened liver. In sectioning, the liver as well as the 

 object is sliced, but they readily separate when placed in alcohol. Beef 

 liver or dog liver is prepared for such purposes by hardening pieces about 

 5x2x2 cm. in size in 95 per cent, alcohol for 24 hours, and then trans- 

 ferring to fresh 95 per cent, alcohol until needed. When much hand 

 sectioning is to be done, a supply of hardened liver should be kept on 

 hand. Many small objects may be held between pieces of pith, and 

 successfully sectioned. 



3. Well Microtomes (Fig. 27) are inexpensive instruments which are 

 used for simple sectioning. Such a microtome consists of a tube in 

 which the object is placed, and at one end of 



which is a plate to guide the razor. The other 

 end is provided with a screw, which, when turned, 

 pushes the contents of the tube above the plate, 

 thus making it possible to cut sections of a uni- 

 form thickness. The object to be cut must be 

 firmly fixed in the well. Such tissues as kidney, 

 liver, spleen, hard tumors, cartilage, etc., may be 

 held sufficiently rigid by wedging small slabs of 

 carrot, turnip, pith, or hardened liver in about 

 them. These supporting substances must, of 

 course, rest squarely against the bottom of the 

 well. Soft tissues, such as soft tumors or brain, 

 must be imbedded. Three parts of paraffin and 

 one part of vaselin melted together and thoroughly 

 mixed makes a very good imbedding-mass for a 

 well microtome. To imbed, warm the microtome 

 slightly and fill the well with the imbedding mix- 

 ture. Remove all liquid from the surface of the 

 tissue, and pass it below the surface of the mixture 

 just as it begins to harden around the edges. When the imbedding 

 mass has become cold the sections are cut in the ordinary way. 



4. Temporary Mounts may be made directly from water after staining 

 by using glycerin as a mounting-medium. Transfer the saction to the 

 slide, add a drop or two of glycerin, and a clean cover-glass. 



FIG. 27. Well Microtome. 



