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TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



For the extraction from the diluted solution of an 

 accurately known volume of liquid, Hensen has devised 

 a form of apparatus known as the " Stempelpipette," that 

 is a pipette furnished with a piston (see fig. 6). This 

 instrument consists of a strong- glass tube (B), the under 

 surface of which is cut oif quite evenly. This tube con- 



Fig. 6. 



tains a moveable piston, consisting of alternating cork (c) 

 and metal (m) plates, securely fastened together by two 

 screws. To this piston a metal cylinder (n) is screwed, 

 and" this must exactly fit the glass tube. From this metal 

 cylinder a quantity of metal is cut off so that between it 

 and the glass tube an exactly known volume, say one ccm., 

 remains. In order to do this, first of all a certain quantity 



