BROAPITULAT10N OF THE PAttAFFIN METHOD. 151 



the same author recommends a thin (light yellow) solution of 

 shellac in absolute alcohol. 



276. Clearing and Mounting. The sections having been 

 obtained are generally mounted on a slide in serial order by 

 one of the methods described in the chapter on Serial Section 

 Methods. All that now remains is to get rid of the paraffin 

 and mount or stain as the case may be. The following 

 solvents of paraffin have been recommended for freeing sec- 

 tions from the paraffin with which they are infiltrated : Tur- 

 pentine, warm turpentine, a mixture of 4 parts of essence of 

 turpentine with 1 of kreasote, kreasote, a mixture of turpen- 

 tine and oil of cloves, benzin, xylol, thin solution of Canada 

 balsam in xylol (only applicable to very thin sections), hot 

 absolute alcohol, naphtha, or any other paraffin oil of low 

 boiling point. Any of these may be used, but naphtha and 

 xylol are probably in most respects the best. Toluol may be 

 added to the list, and will be found to work very well. Per- 

 sonally, I prefer naphtha or toluol to anything else ; xylol 

 evaporates rather too quickly, and so does chloroform. 



If the slide be warmed to the melting point of the paraffin, 

 a few seconds will suffice to remove the paraffin if the slide 

 be plunged into a tube of naphtha or toluol. The sections 

 may be mounted direct from the naphtha, or the slide may 

 be brought into a tube of alcohol to remove the naphtha for 

 staining. 



277. Recapitulation of the Paraffin Method, as recommended to 

 be practised. Put into a small test-tube enough oil of cedar to cover your 

 object. On to the oil pour carefully the same quantity of absolute alcohol. 

 Take your (already dehydrated) object and put it carefully into the alcohol. 

 Leave it until it has sunk to the bottom of the cedar oil. Then put it into 

 paraffin kept at melting point in a watch-glass. After a time change the 

 paraffin (i. e. put the object into a fresh watch-glass with clean paraffin) once 

 or twice if the object be at all large. As soon as the object is thoroughly 

 soaked with paraffin, float the watch-glass on cold water. When cool, cut 

 out a block of paraffin containing the object and fix it with a heated needle 

 on a cone of paraffin already mounted on the object-carrier of the microtome. 

 Pare it square, and as close down to the object as possible on all sides except 

 the one turned towards the knife ; this had better have a wall of a milli- 

 metre or two, or more, according to the size of the object, left standing. Set 

 the knife square. Set the block square to the knife-edge. Cut sections in 

 chains or ribbons, collodionising them if necessary. Mount them in serial 

 order on a slide prepared with Schaellibaum's collodion or Mayer's albumin. 

 Warm, and remove the paraffin with naphtha. Stain or mount. 



