FIXING, IMBEDDING, AND STAINING 



47 



sinking from the alcohol into the cedar oil, and this indicates the 

 time when the mixture may be replaced by pure cedar oil. After 

 remaining in the cedar oil for from twelve to twenty-four hours soft 

 paraffin may be added. In from twelve to twenty-four hours hard 

 paraffin may be used, and after a similar period the material may 

 be imbedded in trays in fresh paraffin. It is desirable in this proc- 

 ess to have the material held in little wire-meshed ladles, and thus 

 the change from one grade of infiltrating agent to another is effected 

 by a transfer of the ladle from one vessel to another. In each case 

 the ladle is thrust into the liquid sufficiently to cover the bowl and 

 material. The cedar oil is then more readily displaced, sinking to 



Fig. ii. A Desirable Outfit for Sectioning and Staining 



the bottom, and there are fewer difficulties in sectioning on account 

 of electrification, which is intensified by the presence of oil. 



Xylol is also employed in infiltration, but with some tissues there 

 seems to be a peculiar optical effect produced, and it has no pecu- 

 liar advantages for this purpose. 



Sectioning. When the objects are imbedded they should be so 

 disposed that each, or each group, is far enough from those adjacent 

 co permit of its being readily cut out and attached to the object 

 carrier. When melted to the carrier careful orientation is given. 

 Sectioning is a simple operation with material properly infiltrated, 

 with a sharp razor or microtome blade, and with the laboratory at 

 living-room temperature. Very tough or carbonaceous fungi will 

 never yield satisfactory sections by the paraffin method, but the 

 great majority of the parasitic fungi may be thus treated. There 



