306 APPENDIX. 



The substance in which different tissues should be 

 imbedded varies with the consistency of the tissue. 

 As a rule the imbedding substance should be of 

 about the same degree of hardness as the tissue. 

 Loose tissues, or tissues with cavities, should before 

 imbedding be treated in the manner given on p. 215. 



A still simpler method of imbedding than that given 

 on p. 68 is to take a block of paraffin B, to heat a 

 stout wire over a Bunsen flame and with it to melt 

 the central portion of one end of the paraffin block, 

 in this the tissue is placed, it is turned into the 

 proper position and the bubbles are removed by 

 means of the warmed wire ; since the wire is very 

 easily made so hot that it would injure the tissue, 

 it should be brought into contact with the tissue 

 as little as possible. This method should only be 

 used for dense tissues. 



The paraffin ' blocks' can be made by taking a tube 

 (e.g. of copper) about a foot long and fitted with 

 a piston, the inside of this is oiled a little and 

 the melted imbedding mixture poured into it; 

 it is placed under a tap to solidify the mixture, the 

 column of substance is then pushed out and cut 

 into lengths about an inch and a half long. 



The time the tissue should stay in the various agents 

 given on p. 215, varies with its density. With tissues 

 treated in this manner the following method of im- 

 bedding will be found better than those previously 

 given. Two L-shaped pieces of lead with sides about 

 half an inch high are placed on a glass slide so that the 

 long limb of each is in contact with the short limb of 

 the other ; the enclosed space is about three-fourths 

 filled with the imbedding mixture, a little water 



