158 BACTERIOLOGY. 



being cut into sections. They must be "imbedded," 

 as this process is called. 



Imbedding in celloidin. Most convenient for this 

 purpose is celloidin, a body somewhat similar to col- 

 lodion, soluble in a mixture of equal parts of alcohol 

 and ether, as well as in absolute alcohol. 



After hardening in alcohol the tissue to be imbedded 

 is placed in a mixture of equal parts of absolute alcohol 

 and ether and left there for twenty-four hours. It is 

 then transferred to celloidin. Two solutions of cel- 

 loidin are to be employed, the one a thin solution in 

 a mixture of equal parts of absolute alcohol and ether, 

 the other a thick solution in the same solvent. Into 

 the thin solution, which should be of about the consist- 

 ence of very thin syrup, the tissue is placed from the 

 absolute alcohol and ether, and allowed to remain there 

 for twenty-four hours. It is then placed in the thick 

 solution for about a day. From this it may be removed 

 and placed immediately upon a bit of cork or a block 

 of wood. The adherent celloidin will act as a cement, 

 and as it hardens rapidly, the tissue is soon fast to the 

 cork. It is then left in 60 per cent, alcohol for twenty- 

 four hours to complete the solidification of the celloidin, 

 after which sections may be cut in the way just described 

 for tissues not so treated. 



Imbedding in paraffin. After bits of the tissue not 

 larger than a cubic centimetre have been hardened in 

 the usual way, they are placed in fresh absolute alcohol 

 for twenty- four hours to complete the process. From 

 this they are transferred to pure turpentine, and kept 

 in a warm oven at a temperatare not exceeding 35 to 

 38 C. Here they remain for a time sufficient for them 

 to become thoroughly saturated with the turpentine, as 



