IMBEDDING IN PARAFFINE 83 



one after another, the delicate grating preventing the 

 sections from slipping off, without in any way injuring 

 them ; and when finally it is raised after full completion of 

 the treatment, the sections remain lying in their original 

 order, and the result is a serial preparation (fig. 27) . 



Imbedding in paraffine. This method serves for the pre- 

 paration of finer sections, but is only rarely used in bacte- 

 riology. It is employed for making single sections as well 

 as for series. The pieces of organ are brought into absolute 

 alcohol for twenty-four hours, then into a mixture of chloro- 

 form and alcohol for twenty-four more, and finally for the 

 same length of time into pure chloroform. Xylol, oil of 

 cloves, and oil of turpentine do not yield such good results. 

 If the pieces are saturated with chloroform they should sink 



Nickel-plated grating 



FIG. 27. SECTION STAINER FOR PREPARATIONS IMBEDDED i\ CELLOIDIXE. 



to the bottom in that liquid. After this they are laid in 

 paraffine dissolved by heat in chloroform, and remain in this 

 solution for two or three hours at a temperature of 30-40 C. 

 Finally they are imbedded in paraffine. Little boxes of paper 

 having been made ready and floated on cold water, fluid 

 paraffine is poured into them, and after it has solidified the 

 pieces of organs are laid upon it and covered with more 

 melted paraffine, which liquefies again the surface of the layer 

 already solidified, so that the specimen seems enclosed in a 

 block of the substance. After a few hours this is trimmed 

 to a suitable form with a knife, clamped in the microtome, 

 and sections are cut with the knife transverse or slightly 

 oblique, and without using any moistening fluid. The micro- 

 tome can be arranged to cut sections of any desired thickness. 



G 2 



