4. IMBEDDING TISSUES FOB CUTTING SECTIONS. 



A. rMBEDDING IN CELLOIDIN. 



1. Transfer the hardened tissue from alcohol to equal 

 parts of alcohol and ether, twelve hours or longer. 



2. Into thin celloidin, twelve hours or longer. 



3. Into thicker ceUoidin, thirteen hours or longer. 



4. Into thick ceUoidin (that is, so thick that the 

 specimens but slowly sink to the bottom), twelve hours or 

 longer. 



5. Place specimen with as much ceUoidin as possible 

 cUnging to it upon cork, a small block of wood, or, best, a 

 block of vulcanized flbre.^ With a glass rod add several 

 layers of the thick ceUoidin untU the specimen is quite 

 surrounded, especiaUy toward its base, with perhaps one- 

 eighth inch of ceUoidin. AUow it to remain in the air 

 until a sufQciently thick film forms on the outside, then 



6. Into 50 to 75 per cent, alcohol (the ceUoidin must 

 be beneath the surface of the fluid) to harden; or harden 

 quickly by dropping it into chloroform, and after a few 

 minutes place in alcohol (75 per cent.). 



7. Cut in alcohol. 



B. IMBEDDING IN CELLOIDIN AND PARAFFIN. 

 1 — L See above under A. 



5. Drop into chloroform and keep immersed (by means 

 of a smaU net loosely attached to a wire frame, for in- 

 stance) from six to eight hours. 



6. Place in melted paraflSn^, one to two days; or 

 better, place in a bottle of melted paraffin kept at 55 to 

 CS degrees 0. in a water-bath, attach a suction pump^ and 

 pump untU a few, or no more, bubbles come away from 

 the tissues, from one to three hours. 



iThis may be obtained from the Vulcanized Fibre Co., Wil- 

 mington, Del., and, when cut into small blocks, is admirable for 

 mounting tissues imbedded in celloidin. One may write with a 

 pencil upon the blocks and they readily sink in fluids, thus saving 

 much trouble. 



2Hard and soft paraflSn are mixed in such proportion that the 

 melting point of ;he combined mass is .iboat 52 degrees O. 



3A Chapman water-pump is the simplest and best to use for this 

 purpose. 



