GENERAL METHODS. 33 



three parts by volume of xylol to one part of alcohol, in 

 which they remain twelve to twenty-four hours.* From 

 this they are placed in xylol for twelve to twenty-four hours 

 more. Their complete permeation with xylol may be recog- 

 nized by the preparations becoming transparent. 



I may here remark that chloroform, oil of turpentine, and 

 toluol have been used instead of xylol in this transfer 

 from alcohol to paraffine. But I think it doubtful whether 

 these substances offer any advantage over xylol. How- 

 ever, the above-mentioned mixture of alcohol and xylol is 

 decidedly preferable to the clove-oil formerly used between 

 the alcohol and xylol. 



47. From xylol the objects are transferred to melted 

 paraffine ; but to prevent the collapse which almost always 

 occurs on a direct transfer from xylol to paraffine, it is better 

 to interpolate a solution of paraffine in xylol. I ordinarily 

 proceed in the following manner with the best results. I 

 place in a so-called bird's trough f a mixture of xylol and 

 paraffine which is solid, or at least of a thick consistency, at 

 ordinary temperatures ; an exact statement of proportions is 

 not important here. On this cold and solid paraffine-xylol 

 mixture I place the objects to be cut and pour over them 

 enough pure xylol to cover them. Then I place the dish 

 uncovered on the top of the paraffine oven about to be 

 described, where the mixture melts gradually so that the 

 objects covered with xylol can sink into it. A further con- 

 centration of thexylol-paraffineis brought about by the eva- 

 poration of the xylol. After six to- twenty-four hours I place 

 the objects in a porcelain dish filled with melted paraffine, 

 which I place in the paraffine oven, vrtiile I allow the dish 

 with the xylol-paraffine mixture to cool for future use in 

 the same way. 



The objects remain in a dish full of melted paraffine from 

 twelve to twenty-four hours according to their size, but a 

 longer time is seldom necessary. 



* For all these transfers Steinach's glass drainers are very useful, 

 f [Any small porcelain dish will serve.] 



