MICHOroMY 



Fig. 4. Schematic representation of tissue and 

 plastic bar molded into same block. 



Fig. 5. Schematic representation of tissue in 

 plastic hollow cj^linder chucked for freeze-.section- 

 ing. 



thickness variation of sections, it is highl}^ 

 important to correct for this factor. It is 

 possible to do this by means of plastic dupli- 

 cates. 



A plastic bar (Fig. 4) made of but 3d and 

 methylmethacrylate (15 and 85 per cent, 

 respectively) is used for embedded material. 

 This is formed and embedded in intimate 

 contact with the tissue to be sectioned. For 

 frozen material a hollow cylinder is used, 

 made of butylmethacrylate, which is filled 

 out with the tissue (Fig. 5). In this way one 

 obtains simultaneously a tissue section and 

 a plastic duplicate which may be separated 

 and measured independently, e.g., with in- 

 terference microscopy. The error committed 

 by allowing the setting of the microtome to 

 indicate the thickness of the section is in this 

 way reduced to about one half for em- 



bedded material and to one third for freeze- 

 sectioned material. 



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