70 Animal Micrology 



cneans of rapidly determining the nature of a given tissue, and is very 

 serviceable, especially to the pathologist. The principal objection is 

 that crystals of ice form in the cells and distort them badly. This is 

 avoided when syrup and gum is used for imbedding. 



2. Sections May Be Preserved in alcohol in the usual way after being 

 cut by the freezing method. All trace of gum should be washed out and 

 the sections passed through the grades of alcohol to 83 per cent., where 

 they may remain indefinitely. 



3. Sections of Fresh Tissue May Be Fixed and washed out after cutting 

 if desired. This requires but little time, and the sections will take 

 stain much more satisfactorily after having been subjected to a fixing 

 reagent. 



4. Objects Which Alcohol Would Injure may be sectioned by the freezing 

 method and mounted in aqueous media. 



5. Ether or Rhigolene . is Sometimes Used for Freezing, although the 

 method is more expensive and less satisfactory on the whole than the 

 carbon dioxide method. Fig. 34 shows a common form of freezing 

 attachment used for either of these liquids. 



