LESSON VII. 



SECTION CUTTING AND IMBEDDING. 



1. Preparation of Hardened Tissue for Freez- 

 ing. If the piece of tissue to be cut has been kept in 

 alcohol, place it in 50 p.c. and then in 30 p.c. alcohol, 

 each for about 10 minutes. Remove the tissue to water 

 for 1 to 3 hours in order to extract the alcohol. The 

 extraction is hastened by placing on the warm bath, at 

 about 38 C. Place then in dilute gum 1 for an hour to 

 a day as convenient. 



Successful section cutting depends largely upon 

 using a sharp razor, it should not be markedly hollow 

 ground, or it may bend and give sections consisting of 

 bands of unequal thickness. The razor should be placed 

 flat on a microscope stage, and the edge examined with 



1 The gum solution is prepared by dissolving gum arabic in 

 sufficient warm water to make a freely flowing solution, and filtering 

 through linen. When it is required to keep the piece of tissue in a 

 given position whilst freezing, it may be transferred to a thick 

 solution of gum a few minutes before placing it in the plate of the 

 microtome ; it can then be kept in position by a needle for the short 

 time that elapses before it is frozen. Since gum alone freezes to a 

 hard mass, a little sugar solution may with advantage Be added to it. 



L. 4 



