SECTION CUTTING. 1 23 



illuminated. There are two ways of accomplishing this : by 

 teasing and by cutting sections. 



The easier method is by teasing. To do this a portion of 

 the object is placed on a. slide with the addition of a few 

 drops of water, alcohol, glycerine or neutral salt solution ac- 

 cording to the nature of the specimens and the objects or 

 portions which it is desired to see. Then with two dissecting 

 needles the tissue is teased or pulled into shreds, and then 

 examined under the microscope, or mounted permanently 

 after any desired method. 



Teasing produces good results in fibrous tissue where it is 

 desired to isolate the iibres, as in nerves, muscles, connective 

 tissue, etc. At other times it does not work so well. 



Section cutting is, however, the most universal and in the 

 majority of cases the best method of pre;)aring substances for 

 examination, but at the same time it requires more time to 

 accomplish. The various processes can conveniently be taken 

 up in the following order ; hardening and decalcifying, em- 

 bedding, cutting and freeing from the embedding material. 



Fresh tissues are generally either too soft, or in the case of 

 bones, teeth, scales, and shell too hard to admit of being read- 

 ily cut and hence certain steps must be taken to prepare them 

 for the razor. 



Suppose we have an object, an embryo tadpole for instance, 

 of which we desire to obtain sections. This in its natural con- 

 dition would' be far too soft and must be hardened. This 

 hardening may be accomplished in various ways. The most 

 common method is first to place it for a few hours in weak 

 alcohol (about 40 per cent.) ; it is then transferred to stronger 



