INTRODUCTION TO FIXATION 27 



they often look remarkably lifelike. Embedding in paraffin, how- 

 ever, usually causes serious distortion. 

 Ideally a fixative would leave the volume'of a piece of tissue 



volume as percentage of original volume 



100 200 300 400 



chromium tri oxide 



osmium tetroxide 



mercuric chloride 



formaldehyde 



potassium dichromate 



acetic acid 



Fig. 5. Diagram showing the changes in vohime undergone by 

 gelatine-albumin gel when acted upon for 18 hours by the selected 

 primary fixatives. The latter were used at their standard 



concentrations.-^ 



and of its constituent cells unaltered, and resistant to alteration 

 by fluids in which it was subsequently placed. Many fixatives 

 shrink tissues; some leave them scarcely changed in volume, 

 while others swell them, but in any case the tissue is liable to 

 subsequent shrinkage. 



The results of shrinkage and swelling lend themselves more 



