CHAPTER VIII 



THE VENETIAN TURPENTINE METHOD 



Venetian turpentine is made from the resin of Larix europea. It 

 looks like Canada balsam and in many ways behaves like it; but it is 

 readily soluble in absolute alcohol. Consequently, material can be 

 transferred directly from absolute alcohol to Venetian turpentine, 

 without passing through xylol or any similar reagent. The mounts are 

 as hard and durable as balsam mounts and they become as trans- 

 parent as if a clearing agent had been used. 



While the method was described by Pfeiffer and Wellheim in 1894, 

 it received no recognition in the United States or even in Europe. 

 I made a casual trial of it when preparing the first edition of this book 

 more than thirty years ago ; but the preparations were such miserable 

 failures that the process did not seem worth mentioning. 



The method was next brought to my attention during a demonstra- 

 tion in Strasburger's laboratory at Bonn. He was using preparations 

 of Zijgnema and Spirogyra, the staining of which surpassed anything 

 I had ever seen. He remarked that it was not worth while to consult 

 Pfeiffer and Wellheim 's lengthy article, because his preparations had 

 been made by the authors and no one else had made a success of the 

 method. However, when I returned, I made a careful study of the 

 process, and finally learned to use it successfully. The details as given 

 in that paper were too indefinite for practical use, but, after one has 

 learned the method, the article can be read with profit. 



The practical advantages of the method are the elimination of the 

 dangerous xylol stage, the hard durable mounts, and a greater variety 

 of stains than can be used with glycerin. 



After fixing, washing in water, running up in alcohols from 2| to 

 85 per cent, running back to water, and staining in an aqueous stain, 

 e.g., iron-alum haematoxylin, the process is as follows: 



1. Ten per cent glycerin until concentrated. 



2. Wash the glycerin out thoroughly in 95 per cent alcohol. 



3. Complete the dehydration in 100 per cent alcohol. 



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