Journal of Applied Microscopy. 



11 



be filtered into the beakers kept in the 

 paraffin bath. After the tissues are 

 thoroughly permeated with the xylol, it 

 is poured off and the soft paraffin added. 

 The tube vial, or other dish containing- 

 the tissues and the paraffin, is now 

 placed in a paraffin bath in the compart- 

 ment containing the soft paraffin, where 

 it remains for two to four hours, at 

 the end of which time the soft paraffin is 

 poured back into the beaker containing 

 the soft paraffin, as it may be used over 

 and over again, and hard paraffin added; 

 the tissues are then again placed in the 

 bath, where they remain for four to 

 twenty-four hours. Small pieces are 

 usually well permeated in four hours; a 

 longer stay is, however, not necessarily 

 detrimental, if the temperature of the 

 bath does not exceed the melting point 

 of the hard paraffin by two to four 

 degrees. The final step in paraffin im- 

 bedding is as follows: Two metallic Li"s 

 are placed together on a glass or metallic 

 plate in such a way as to form a rectan- 

 gular box. Fig. II. This is filled with 



Fig. II. 



the hard paraffin. Before the paraffin 

 cools the piece of tissue to be imbedded 

 is placed with one of its fiat surfaces 

 against one end of the box. If several 

 pieces of tissue are to be mounted, 

 a piece may be thus- placed in each end 

 of the box. While transferring the tis- 

 sues from the hard paraffin to the 

 paraffin in the imbedding box, they 

 should be handled with forceps, the ends 

 of which have been warmed in a flame. 

 As soon as the paraffin in which the tis- 

 sues are imbedded has cooled sufficiently 

 to allow the formation of a film over the 

 paraffin, the imbedding box is placed in 

 a dish of cold water. This cools the 

 paraffin quickly and prevents its crystal- 

 lization. A stay of five to ten minutes 

 in the cold water hardens the paraffin 

 so that the L's may be removed and the 

 paraffin box taken from the plate. It is 

 well to place the paraffin block thus ob- 

 tained back into the cold water for a 

 while, so that it may become hard all the 

 way thi'ough. If the rectangular box 

 formed by the L's is about an inch long, 

 the resulting paraffin block, containing 

 the tissue in one or both ends, will be 

 long enough to be clamped at once In the 

 microtome. 



If It is not convenient to have a paraffin 

 bath, a simpler apparatus. Fig. Ill, viz.. 



a paraffin imbedding table, may be used. 

 This consists of a copper plate of tri- 

 angular shape, about eighteen inches 

 long and eix to eight inches wide at the 

 end, supported on three legs. A Bunsen 

 burner is placed under the acute angle, 

 the heat being transmitted through the 

 metal. The hard and soft paraffins are 



Fig. III. 



placed in small glass dishes. (The 

 paraffin should be filtered before using.) 

 The dishes containing the hard and soft 

 paraffin are now placed on the copper 

 plate, and moved toward and away from 

 the flame, until a spot is found where 

 the paraffin in both the dishes just 

 nielts. It hardly needs to be stated, that 

 the dish containing the hard paraffin 

 needs to b'? placed nearer the flame than 

 the one containing the soft paraffin. If 

 the flame and plate are placed in about 

 the same relative positions, and about 

 the same size flames used, and currents 

 of air are guarded against, the places 

 where the dishes containing the hard and 

 soft paraffin are to be placed, ascer- 

 tained as above directed, will remain 

 practically the same. As soon as the 

 soft paraffin is melted, the tissues are 

 taken from the xylol and placed in it, 

 where they remain from one to two 

 hours. They are then transferred to the 

 dish contajning the hard paraffin, in 

 which they remain several hours. The 

 tissues are then "blocked" in the man- 

 ner above described. It is well to use 

 small and thiii pieces when imbedding 

 in this way. 



Celloidin Imbedding. — The best and 

 most convenient celloidin to use in micro- 

 scopical work is Scherring's granular 

 celloidin, put up in one-ounce bottles. 

 Of this a stock or thick solution is pre- 

 pared by dissolving six parts of the cel- 

 loidin in one hundred parts of equal parts 

 of absolute alcohol and ether. Of this, 

 when required, a thin solution is pre- 

 pared, by diluting a quantity of the stock 

 solution with an equal quantity of the 

 ether and alcohol solution (equal parts). 



Method of Imbedding. — The hardened 

 tissues are cut into small pieces, which 

 should net be much more than one-eighth 

 of an inch in thickness and having a sur- 

 face area of about one-half square inch. 

 The pieces to be imbedded are placed for 

 twenty-four hours in absolute alcohol; 

 are then transferred for twenty-four 



