EMBEDDING. 



43 



turpentine, toluol, or xylol is to be preferred. The turpentine or 

 xylol penetrates into the tissue, displaces the alcohol, and makes 

 the tissue itself transparent. If the tissue be very small, this will 

 be done in an hour or so ; if it be larger, of course a longer time 

 will be required. Thus the time may vary, according to the size 

 and nature of the tissue, from, one to six hours. 



Transfer the specimens from the clarifying medium, and place 

 them in the melted paraffin, where they may remain 2-10 hours, 

 according to the size and nature of the tissue. By the end of that 

 time they will be thoroughly impregnated or saturated with the 

 paraffin. 



For delicate tissues, however, it is better not to transfer them 

 direct from the clarifying medium to pure paraffin, but to place 

 them first of all in a mixture of toluol and paraffin, or turpentine 

 and paraffin, for an hour or two. In the thermostat at 5o-55 C. 

 the toluol gradually evaporates, so that nearly pure paraffin remains, 

 and the saturation with paraffin has been accomplished more 

 gradually. The object is then finally placed in pure paraffin for 

 several hours. 



Some prefer chloroform as a clarifying agent and as a solvent for 

 paraffin instead of toluol or turpentine. Objects transferred from 

 absolute alcohol at first float on the surface of the chloroform, but 

 as the latter penetrates them and displaces the alcohol they sink. 

 They are then embedded in a chloroform paraffin mixture and 

 finally in pure paraffin. 



The time (in hours) required for immersion in the several fluids 

 for pieces of tissue of various sizes is approximately as follows 

 (Bohm and Oppel) : 



Objects may remain longer in the paraffin without damage, 

 provided they have been completely dehydrated. 



