64 Animal Micrology 



ture of equal parts of origanum oil and xylol for a few hours, and finally 

 to pure xylol. Proceed from this point as in ordinary paraffin infiltration 

 and sectioning, although the length of time in the paraffin bath should 

 be curtailed as much as possible to avoid making the celloidin brittle. 



9. To Transfer Celloidin Sections from the Knife it is an excellent plan 

 to use a paper spatula; a bit of postal card held in the cleft end of 

 a small stick answers very well. Press the paper down evenly on the 

 section and then slide it off the edge of the knife. The section adheres 

 to the paper. In carrying loose sections from one fluid to another an 

 ordinary section lifter may be used or a glass rod around which the sec- 

 tion is allowed to curl answers very well. 



10. Objects Stained in Bulk May Be Cleared while Yet in the Block, then 

 sectioned, and mounted without passing back into the alcohols. After 

 the block of celloidin has hardened sufficiently in chloroform it is trans- 

 ferred directly to the clearer (cedar oil, or a mixture of oil of thyme 

 3 parts and castor oil 1 part). In cutting objects thus cleared the knife 

 must be flooded with the clearer instead of alcohol. Do not allow the 

 sections to become dry. If it is desired to use this method for a celloidin 

 block which has already been preserved in 70 to 83 per cent, alcohol, the 

 block must pass through 95 per cent, alcohol (1 to 2 hours) before it is 

 placed in the clearer. 



11. Collodion instead of Celloidin is used by some workers. Celloidin, 

 in fact, is only a patent preparation of collodion, which is a solution of 

 gun cotton in ether and strong alcohol. Thin and thick solutions are 

 employed and the method is in every respect similar to the celloidin 

 method. Collodion is cheaper than celloidin. 



12. Fixing Serial Celloidin Sections to the Slide is accomplished, (1) by 

 covering the sections, when mounted in proper order, with a strip of 

 tissue paper which is then bound fast by wrapping thread around it. 

 Lee (Microtomist's Vade-Mecum, 6th ed., p. 144) recommends (2) the 

 albumen method for celloidin sections as well as for paraffin. (3) If the 

 sections on the slide are carefully flooded with 95 per cent, alcohol two 

 or three times, this drained off and followed by a small amount of ether- 

 alcohol or ether fumes until the edges of the sections begin to soften per- 

 ceptibly (10 to 20 seconds), the sections will generally adhere to the slide 

 sufficiently when the celloidin becomes hard again upon exposure to the 

 air (30 seconds) after the ether-alcohol has been drained off; they must 

 then be immersed in 95 per cent, alcohol before any further steps are 

 taken. 



13. Gilson's Rapid Celloidin Process (Lee, The Microtomist's Vade- 

 Mecum, 6th ed., p. 131) is a very valuable one because of the great sav- 

 ing of time. After dehydration the object is saturated with ether and 

 finally placed into a test-tube containing thin celloidin. The lower end 



