2Q MICRO-ORGANISMS AND DISEASE [chap. 



cloves, and finally on to a glass slide, on which they are 

 mounted in the usual manner with Canada-balsam solution, 

 the excess of clove-oil being previously drained off. 



It is advisable, although not absolutely essential, to keep 

 the sections in a well-spread-out condition for a few seconds 

 in alcohol before placing them into the dye. 



For the preparation of mounted stained specimens by the 

 rocking microtome the following method is used in my 

 laboratory : 



Small pieces of. tissue are put in Miiller's fluid ^ and 

 changed on the second and third day, are then allowed to 

 stand for seven days, then put in two-thirds methylated 

 spirit and one-third water, change after twenty-four hours to 

 absolute alcohol, and allow to properly harden. 



Embedding in Paraffin. 



Selected piece of tissue is then treated as follows : 



1. Absolute alcohol, twenty-four hours. 



2. Absolute alcohol and cedar wood oil, equal parts, 

 twelve hours. 



3. Cedar wood oil, twelve hours. 



4. Paraffin liquid, 50 to 52" C, bath No. i, twelve hours. 



5. Paraffin liquid, 50 to 52° C, bath No. 2, twelve hours. 



6. Pour paraffin in a small box of brass or lead and place 

 tissue in it, when set take the paraffin block out of the box, 

 trim and fix on rocking microtome. Cut number of sec- 

 tions and float into warm water at 30° C. Fix sections on 

 cover-glasses, and allow to dry in incubator at 37° C. 



7. Xylol, five minutes. 



' Glanders tissues are best placed at once in absolute alcohol. 



