460 NORMAL HISTOLOGY AND ORGANOGRAPHY. 



celloidin does not feel sticky to the touch. The 

 usual time will be ten to twenty minutes. 



(d) Transfer to Chloroform Vapor. Pour a little 

 chloroform over the bottom of a dish. Set the 

 blocks in this so that the liquid does not reach the 

 tissue. Cover tightly and leave for thirty minutes. 



(e) Transfer to chloroform liquid by immersing the 

 tissue. Time, thirty minutes. 



(/) Transfer to 80% alcohol, where blocks may be 

 left permanently. 



6. Imbedding with Paraffin or Fusion Method. 



(a) Intermediate Stage. The tissue is taken out of 

 absolute alcohol, where it has been thoroughly 

 dehydrated, and is then treated with some fluid 

 that is miscible on the one hand with absolute 

 alcohol, and on the other with paraffin. Liquids 

 used are 



(1) Chloroform. 



(2) Cedar-wood oil. 



(3) Turpentine. 



(4) Xylol. 



Tissues left in oils become brittle. From one to two 

 hours are usually sufficient, depending upon the size 

 of the piece to be imbedded. Chloroform will harden 

 the tissue to a less degree than the other fluids. 



(b) Melted Paraffin. The melting-point of paraf- 

 fin should vary according to the room temperature 

 where the sections will be cut. The following table 

 gives the relation of melting-point of paraffin to this 

 temperature : 



Paraffin melting- point. Room temperature. 



45 C. . 15 to 17 C. or 60 to 65 F. 



48 C 22 C. or 70 F. 



55 C. . . 24 C. or 75 F. 



