THE ELEMENTS OF VEGETABLE HISTOLOGY 



1 . Place the specimens in saturated solution of paraffin in 



chloroform or xylol for six to twelve hours. 



2. Transfer specimens to melted paraffin (bath A) for two to 



four hours. 



3. Transfer specimens to melted paraffin (bath B) for four to 



eight hours. 



Embedding. — The last process in the infiltration 

 method consists in surrounding the specimen with 

 sufficient paraffin to support it during sectioning. 



Metal or paper molds are 

 used for this purpose. 

 The metal molds (Fig. 

 1) are adjustable for 

 different sized specimens 

 and permit more rapid 

 chilling of the paraffin 

 than is possible with 

 paper molds. Melted 

 paraffin is poured into 

 the mold so as to form a layer about 8 mm. in 

 depth. The mold is then placed in a shallow dish 

 of cold water so that the paraffin on the bottom 

 and sides will congeal quickly. The specimen is 

 placed in the soft paraffin in the center of the mold, 

 care being taken to place it so that the surface 

 from which the sections are to be cut is toward 

 the narrow end of the block and that the entire speci- 

 men is parallel with the long side of the mold. This 

 orientation, or proper placing of the specimen, is 

 necessary if one desires to obtain exact transverse 

 sections and wishes to avoid frequent shifting of the 

 block while cutting. After the specimen is properly 

 placed, melted paraffin is poured into the mold so that 

 the layers of paraffin on each side of the specimen 



Fig. 1— Paraffin Mold. 



(Bausch & Lomb.) 



