150 PATHOGENIC BACTERIA. 



The ordinary methods of imbedding suffice. The sim- 

 pler of these are probably as follows: 



I. Celloidin. — From the hardening reagent (if other 

 than absolute alcohol) — 



12-24 hours in 95 per cent, alcohol, 



6-12 " " absolute alcohol, 

 12-24 " " thin celloidin (consistence of oil), 



6-12 " " thick celloidin (consistence of molasses). 



The solutions of celloidin are made in equal parts of 

 absolute alcohol and ether. 



Place upon a block of dry wood, allow to evaporate 

 until the block can be overturned without dislodging the 

 specimen ; then place in 70-80 per cent, alcohol until 

 ready to cut. The knife must be kept flooded with alco- 

 hol while cutting. 



II. Paraffin — 



12-24 hours in 95 per cent, alcohol, 

 6-12 " " absolute alcohol, 



4 u " chloroform, benzole, or xylol, 

 4-8 " "a saturated solution of paraffin in one of 

 the above reagents. 



Place in melted paraffin in an oven or paraffin water- 

 bath, at 50°-6o° C, until the volatile reagent is all evap- 

 orated, and the tissue impregnated with paraffin. Im- 

 bed in freshly melted paraffin in any convenient mould. 

 In cutting, the knife must be perfectly dry.- 



When it is necessary, subsequently, to remove the im- 

 bedding material, dissolve the paraffin in chloroform, 

 benzole, xylol, oil of turpentine, etc., which in turn can 

 be removed with 95 per cent, alcohol. 



Celloidin is soluble in absolute alcohol, ether, and oil of 

 cloves. It is very convenient to fasten the cut sections upon 

 the slide — paraffin sections by Myer's glycerin-albumin 

 mixture, oil of cloves and collodion or gum arabic solu- 

 tion; celloidin sections by firmly pressing filter paper 

 upon them and rubbing hard, then allowing a little 

 vapor of ether to run upon them. 



