22 Animal Micrology 



indefinitely. Other good clearers after alcohol are oil of origanum, 

 sandal-wood oil, oil of cloves, toluol, oil of bergamot, anilin oil 

 (for watery specimens) , carbolic acid (for watery specimens), and 

 beechwood creasote. Clove oil should not be used for celloidin 

 sections because it dissolves celloidin. It is also inapplicable 

 ordinarily after most anilin dyes because of its tendency to 

 extract them. Among the best reagents for celloidin sections 

 are cedar- wood oil, carbol-xylol, oil of origanum, creasote, and 

 Eycleshymer's clearer (memorandum 4, chap. vii). 



While "clearing" refers especially to the rendering trans- 

 parent of tissue elements, and dealcoliolization to the removal of 

 alcohol previous to imbedding in paraffin, very frequently the 

 same reagent is used for either purpose and the term "clearing" 

 has come to be used in either sense. 



MOUNTING 



After tissues have been cleared the final step is to mount them 

 in some suitable medium for preservation and inspection. 



If tissues are to be mounted directly from water or aqueous 

 media, glycerin, glycerin-jelly, or Farrant's solution is used ordi- 

 narily. If the alcoholic dehydration method is employed, balsam 

 or gum damar is the final mounting medium. The balsam or 

 damar is dissolved commonly in xylol, although turpentine, chlo- 

 roform, or benzol may be used as the solvent. Xylol-balsam is 

 the most satisfactory for ordinary purposes. 



IMBEDDING 



In order to section tissues or objects satisfactorily it is fre- 

 quently necessary to imbed them in a suitable matrix. Simple 

 imbedding consists in merely surrounding the object by an 

 appropriate medium to hold it in place while it is being cut. In 

 interstitial imbedding the object is saturated (infiltrated} with 

 the imbedding substance which, when all cavities and inter- 

 sticies are filled, is caused to set; thus it supports all parts of 

 the tissue and holds the components in place when sections are 

 made. Infiltration imbedding is of great importance to micros- 

 copists arid much of the space of the present book is given up to 



