l6 NORMAL HISTOLOGY. 



band around it. The specimen having been soaked 

 in celloidin, is placed in the box, adjusted as to 

 position, and the box filled with celloidin. After 

 allowing it to stand in the air until a firm pellicle has 

 formed, it is immersed in 80 per cent, alcohol. To 

 prevent the boxes floating on the surface, fasten a bit 

 of lead to the bottom of the box with a pin. 



Specimens imbedded in celloidin should be pre- 

 served in 80 per cent, alcohol, as strong alcohol 

 softens the imbedding mass. 



Paraffin. A paraffin having a melting point be- 

 tween 48 and 50 C. should be used. The specimen 

 to be imbedded should be small. After the speci- 

 men has been thoroughly dehydrated in strong 

 alcohol, it is placed in chloroform until the former 

 has been replaced by the latter. It is then trans- 

 ferred to a mixture of one third paraffin and two 

 thirds chloroform and placed in a water-oven at a 

 temperature of 50 C. for twelve hours ; it is now 

 transferred to melted paraffin and allowed to remain 

 in the water-oven until thoroughly impregnated. 

 This will require from twelve to twenty-four hours, 

 according to the size of the specimen. The speci- 

 men is then imbedded in a paper box, in the same 

 manner as described under celloidin. After the 

 paraffin has become solid, the paper is removed and 

 the paraffin block is mounted on a cork with melted 

 paraffin, or clamped in the microtome clamp. Sec- 

 tions should be cut with a dry knife. 



