10 PRACTICAL MICROSCOPY. 



rally opaque structures may be illuminated by transmitted light. 

 This becomes an easy matter with such tissues as cartilage; but some, 

 like bone, are much too hard to admit of cutting, and others are as 

 much too soft; so that while certain tissues must be softened, the 

 majority must be hardened. Fortunately, both of these conditions 

 may be secured without in any way altering the appearance or rela- 

 tions of the structures. Hardening processes, from necessity, become 

 a prominent feature in histological work; but I propose here to indi- 

 cate some of the more useful methods of section-cutting, reserving 

 the hardening processes for another place. 



FREE-HAND SECTION CUTTING. 



My students, when ready for this work, are provided with some 

 tissue which has been previously hardened. We will take, for ex- 

 ample, a piece of liver which has been rendered sufficiently firm for 

 our work by immersion in alcohol, and proceed to direct the steps in 

 obtaining suitable sections by the simple free-hand method. 



FIG. 3. FREE-HAND SECTION CUTTING. 



I wish to strongly emphasize the importance of this mode of cut- 

 ting. A moderate amount of practice will render the microscopist 

 independent of all appliances, save those of the most simple character 

 and which are always obtainable. 



An ordinary razor, with keen edge, and a shallow dish, preferably 

 a saucer, partly filled with alcohol are required. The razor best 



